Script Brushes: Errors sometimes reported as just "C++ exception"

[ihm-tswow]

Transferred from tswow#31

Errors, especially when thrown from scripts global scope, are sometimes just printed as "C++ exception" in the log. This is not very helpful for scripters, as they don't even know what line their error ocurred on. Usually, this seems to relate to invalid arguments being passed to functions. Some errors do report correctly with error message and line numbers.