BUG: 15639 prevent modulo-by-zero error
When all annotations where deleted, a SIGFPE exception was triggered by a modulo-by-zero operation. Added check to not compute color map color when there are no annotations to prevent this error.
When all annotations where deleted, a SIGFPE exception was triggered by a modulo-by-zero operation. Added check to not compute color map color when there are no annotations to prevent this error.