Improve processing of invalid calculations

[sam57719]

1. For example:
   1//////////////////////////////
   Process all the tokens before erroring.
   This should be changed to realize it's invalid earlier and not process all the tokens.

2. For example:
   //////////////////////////1
   Actually raises an exception as one of the divide nodes is being processed as NoneType
   This should be fixed in the parser to produce a SyntaxError and stop parsing instead of getting into the interpreter