Enables parenthesis evaluation

@BrettASwift @kadst43 Had it mostly working before... instituting the graph failure check made this a lot easier. Still should have a few people mess with it a bit.
The line below (line 274): `if ( isNaN( dropdown_value ) ){` doesn't work. If it's empty, it evaluates to a number. Try `if ( isNaN( dropdown_value ) || dropdown_value === "" ){`