Checking to see if HKCU key exists. Fixes #1685

@johnsimons - can you see if this is what you had in mind? 
Essentially, I am not writing to the key, if the reg key doesn't exist. 

I tested the script separately turning off the Out-Nulls. I did not verify the whole deal of building a nuget package and testing it out. Let me know if this looks ok to you.