Protect apk from decompiling : facebook messenger

I tried to get xml from com.facebook.orca_3.1.2-release.apk with commeand apktool.bat d com.facebook.orca_3.1.2-release.apk I use apktool 1.5.2

I get an exception:

apktool.bat d com.facebook.orca_3.1.2-release.apk
I: Baksmaling...
I: Loading resource table...
I: Loaded.
I: Decoding AndroidManifest.xml with resources...
I: Loading resource table from file: C:\Users\apktool\framework\1.apk
I: Loaded.
W: Could not decode attr value, using undecoded value instead: ns=android, name=
hardwareAccelerated, value=0xffffffff
W: Could not decode attr value, using undecoded value instead: ns=android, name=
parentActivityName, value=0x00000067
Exception in thread "main" java.lang.NullPointerException
        at java.io.Writer.write(Unknown Source)
        at brut.androlib.res.util.ExtMXSerializer.writeAttributeValue(ExtMXSeria
lizer.java:38)
        at org.xmlpull.mxp1_serializer.MXSerializer.attribute(MXSerializer.java:
673)
        at org.xmlpull.v1.wrapper.classic.XmlSerializerDelegate.attribute(XmlSer
ializerDelegate.java:106)
        at org.xmlpull.v1.wrapper.classic.StaticXmlSerializerWrapper.writeStartT
ag(StaticXmlSerializerWrapper.java:267)
        at org.xmlpull.v1.wrapper.classic.StaticXmlSerializerWrapper.event(Stati
cXmlSerializerWrapper.java:211)
        at brut.androlib.res.decoder.XmlPullStreamDecoder$1.event(XmlPullStreamD
ecoder.java:80)
        at brut.androlib.res.decoder.XmlPullStreamDecoder.decode(XmlPullStreamDe
coder.java:130)
        at brut.androlib.res.decoder.XmlPullStreamDecoder.decodeManifest(XmlPull
StreamDecoder.java:144)
        at brut.androlib.res.decoder.ResFileDecoder.decodeManifest(ResFileDecode
r.java:131)
        at brut.androlib.res.AndrolibResources.decode(AndrolibResources.java:218
)
        at brut.androlib.Androlib.decodeResourcesFull(Androlib.java:115)
        at brut.androlib.ApkDecoder.decode(ApkDecoder.java:114)
        at brut.apktool.Main.cmdDecode(Main.java:146)
        at brut.apktool.Main.main(Main.java:77)

I would like to know how to do it, how to protect xml from decrypting, because even with proguard, I can use reverse engeneering in my own apk.