Hololens emulator showing NullReferenceException

I'm trying to run a Hello World kind of problem for a HoloLens on emulator but it is showing error:

The following unexpected error occurred during bootstrapping stage 
'Connecting to the device '<device>'.': NullReferenceException - Object reference not set to an instance of an object. [0x80004003] 

I have tried making a new project, reinstalling emulator and checked Hyper-V on my system

Please refer to the Troubleshooting section of https://docs.microsoft.com/en-us/windows/mixed-reality/using-the-hololens-emulator. I suspect you're hitting an installation issue where XDE is installed to the wrong folder. The documentation includes a solution for this. Please let me know if this does not resolve the issue.