add try/except clauses around null invocations that were meant to test that the preprocessor already ran, such that we are robust to typical errors if that is true. Tested by using the original code.
add try/except clauses around null invocations that were meant to test that the preprocessor already ran, such that we are robust to typical errors if that is true. Tested by using the original code.

BBN-Q/pyqgl2,BBN-Q/pyqgl2