.Net Runtime crash

When I try to run my C# application, it runs fine on my computer (from VS and when running the exe from the explorer). However, if I try to launch the application on any other computer, it crashes with two Errors, there is no message, these are from the Event Viewer Log. And I know what a null reference exception is, but MY computer runs the program, but other computers wont. I am asking WHAT is missing for the NullReferneceException to trigger!

First Log:

Application: FolderSearch.exe
Framework Version: v4.0.30319
Description: The process was terminated due to an unhandled exception.
Exception Info: System.NullReferenceException
   at FolderSearch.MainWindow..ctor()

Exception Info: System.Reflection.TargetInvocationException
   at System.RuntimeTypeHandle.CreateInstance(System.RuntimeType, Boolean, Boolean, Boolean ByRef, System.RuntimeMethodHandleInternal ByRef, Boolean ByRef)
   at System.RuntimeType.CreateInstanceSlow(Boolean, Boolean, Boolean, System.Threading.StackCrawlMark ByRef)
   at System.RuntimeType.CreateInstanceDefaultCtor(Boolean, Boolean, Boolean, System.Threading.StackCrawlMark ByRef)
   at System.Activator.CreateInstance(System.Type, Boolean)
   at System.RuntimeType.CreateInstanceImpl(System.Reflection.BindingFlags, System.Reflection.Binder, System.Object[], System.Globalization.CultureInfo, System.Object[], System.Threading.StackCrawlMark ByRef)
   at System.Activator.CreateInstance(System.Type, System.Reflection.BindingFlags, System.Reflection.Binder, System.Object[], System.Globalization.CultureInfo, System.Object[])
   at System.Activator.CreateInstance(System.Type, System.Object[])
   at System.Xaml.Schema.SafeReflectionInvoker.CreateInstanceCritical(System.Type, System.Object[])
   at System.Xaml.Schema.SafeReflectionInvoker.CreateInstance(System.Type, System.Object[])
   at System.Xaml.Schema.XamlTypeInvoker.CreateInstance(System.Object[])
   at MS.Internal.Xaml.Runtime.ClrObjectRuntime.CreateInstanceWithCtor(System.Xaml.XamlType, System.Object[])
   at MS.Internal.Xaml.Runtime.ClrObjectRuntime.CreateInstance(System.Xaml.XamlType, System.Object[])
   at MS.Internal.Xaml.Runtime.PartialTrustTolerantRuntime.CreateInstance(System.Xaml.XamlType, System.Object[])
   at System.Xaml.XamlObjectWriter.Logic_CreateAndAssignToParentStart(MS.Internal.Xaml.Context.ObjectWriterContext)
   at System.Xaml.XamlObjectWriter.WriteStartMember(System.Xaml.XamlMember)
   at System.Xaml.XamlWriter.WriteNode(System.Xaml.XamlReader)
   at System.Windows.Markup.WpfXamlLoader.TransformNodes(System.Xaml.XamlReader, System.Xaml.XamlObjectWriter, Boolean, Boolean, Boolean, System.Xaml.IXamlLineInfo, System.Xaml.IXamlLineInfoConsumer,
MS.Internal.Xaml.Context.XamlContextStack`1<System.Windows.Markup.WpfXamlFrame>, System.Windows.Markup.IStyleConnector)
       at System.Windows.Markup.WpfXamlLoader.Load(System.Xaml.XamlReader, System.Xaml.IXamlObjectWriterFactory, Boolean, System.Object, System.Xaml.XamlObjectWriterSettings, System.Uri)
       at System.Windows.Markup.WpfXamlLoader.LoadBaml(System.Xaml.XamlReader, Boolean, System.Object, System.Xaml.Permissions.XamlAccessLevel, System.Uri)
       at System.Windows.Markup.XamlReader.LoadBaml(System.IO.Stream, System.Windows.Markup.ParserContext, System.Object, Boolean)
       at System.Windows.Application.LoadBamlStreamWithSyncInfo(System.IO.Stream, System.Windows.Markup.ParserContext)
       at System.Windows.Application.LoadComponent(System.Uri, Boolean)
       at System.Windows.Application.DoStartup()
       at System.Windows.Application.<.ctor>b__1_0(System.Object)
       at System.Windows.Threading.ExceptionWrapper.InternalRealCall(System.Delegate, System.Object, Int32)
       at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(System.Object, System.Delegate, System.Object, Int32, System.Delegate)
       at System.Windows.Threading.DispatcherOperation.InvokeImpl()
       at System.Windows.Threading.DispatcherOperation.InvokeInSecurityContext(System.Object)
       at System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)
       at System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)
       at System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object)
       at MS.Internal.CulturePreservingExecutionContext.Run(MS.Internal.CulturePreservingExecutionContext, System.Threading.ContextCallback, System.Object)
       at System.Windows.Threading.DispatcherOperation.Invoke()
       at System.Windows.Threading.Dispatcher.ProcessQueue()
       at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr, Int32, IntPtr, IntPtr, Boolean ByRef)
       at MS.Win32.HwndWrapper.WndProc(IntPtr, Int32, IntPtr, IntPtr, Boolean ByRef)
       at MS.Win32.HwndSubclass.DispatcherCallbackOperation(System.Object)
       at System.Windows.Threading.ExceptionWrapper.InternalRealCall(System.Delegate, System.Object, Int32)
       at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(System.Object, System.Delegate, System.Object, Int32, System.Delegate)
       at System.Windows.Threading.Dispatcher.LegacyInvokeImpl(System.Windows.Threading.DispatcherPriority, System.TimeSpan, System.Delegate, System.Object, Int32)
       at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr, Int32, IntPtr, IntPtr)
       at MS.Win32.UnsafeNativeMethods.DispatchMessage(System.Windows.Interop.MSG ByRef)
       at System.Windows.Threading.Dispatcher.PushFrameImpl(System.Windows.Threading.DispatcherFrame)
       at System.Windows.Threading.Dispatcher.PushFrame(System.Windows.Threading.DispatcherFrame)
       at System.Windows.Application.RunDispatcher(System.Object)
       at System.Windows.Application.RunInternal(System.Windows.Window)
       at System.Windows.Application.Run(System.Windows.Window)
       at FolderSearch.App.Main()

And the second Log:

Faulting application name: FolderSearch.exe, version: 1.0.0.0, time stamp: 0x59b7a459
Faulting module name: KERNELBASE.dll, version: 10.0.14393.1532, time stamp: 0x5965adf8
Exception code: 0xe0434352
Fault offset: 0x000da9f2
Faulting process id: 0x2f30
Faulting application start time: 0x01d32ba71864fe5a
Faulting application path: C:\temp\FolderSearchRelease\FolderSearch.exe
Faulting module path: C:\Windows\System32\KERNELBASE.dll
Report Id: 46e410b2-b20a-41c1-817a-883f64d01596
Faulting package full name: 
Faulting package-relative application ID: 

dotnet --info gives the following information:

.NET Command Line Tools (1.0.4)

Product Information:
 Version:            1.0.4
 Commit SHA-1 hash:  af1e6684fd

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.14393
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\PROGRAM FILES\DOTNET\sdk\1.0.4

My .Net Version is 4.6.01586, I targeted the application at 4.5.2 (Visual Studio defaulted to this) and I use VS 2017. It is a WPF program.

How can I fix this? There is no such thing as "..ctor()" in my program!