Object reference not set to an instance of an object - Sort of Error

I was having a look at why scaffold option is missing from my controllers options and found some information on additional references I didn't have in my references.  Added and updated to remove warnings and now I am getting this error:

Object reference not set to an instance of an object.	Eva804	C:\Program Files (x86)\MSBuild\Microsoft\VisualStudio\v14.0\DotNet\Microsoft.DotNet.Common.Targets	262	

Okay seen this before on my own code and usually means I have stuffed it up.  But this error is showing on:

<Dnx
      RuntimeExe="$(SDKToolingExe)"
      Condition="'$(_DesignTimeHostBuild)' != 'true'"
      ProjectFolder="$(MSBuildProjectDirectory)"
      Arguments="$(_BuildArguments)"
      />

Which is in the code generated by Visual Studio as part of the framework.  I don't understand why this is generating an error or what to do to fix it?