I think, that Visual Blitz, Blitz3D needs to have better debugging help, such as these types of situations, would be much better if it said, variable used before dimensioned. or Attempted usage of an undefined variable, I don't know how hard it would be to put this debugging in, but it desperately needs it, I have realized here lately just how hard it is to debug a program with 1000's of lines of code in it, even with debug mode turned on.
Its not Visual Blitz's fault - it can only report errors as they are returned from the compiler.