ImproveDoWhile

Remove not needed \t and spaces
Say if 'test' socket empty
Slightly better 'socket null' message

TODO? Would really like to provide more info to user.
eg. What type of block requires what type of value in what type of
socket.
remove accidental BlockException import
Merge pull request #86 from TonyCallear/ImproveDoWhile

"do while" block bugfix