catch broken vector member access

catch broken vector member access

These kinds of expressions currently cannot be handled
without pionter support in the qcvm without scanning the
ast from within ast_member::codegen for an assignments as
seen in the added test case.

This change makes code like that return a pointer type which
will cause an error that we did not get a vector or field
back. With pointer support this pointer could actually be
used instead.

So at least it shouldn't silently produce broken code
anymore.

Signed-off-by: Wolfgang Bumiller <wry.git@bumiller.com>