Fortran: avoid several NULL pointer dereferences during error recovery

gcc/fortran/ChangeLog:

	PR fortran/102332
	* expr.c (gfc_get_variable_expr): Avoid NULL pointer dereferences
	during handling of errors with invalid uses of CLASS variables.
	* match.c (select_type_set_tmp): Likewise.
	* primary.c (gfc_match_varspec): Likewise.
	* resolve.c (resolve_variable): Likewise.
	(resolve_select_type): Likewise.

gcc/testsuite/ChangeLog:

	PR fortran/102332
	* gfortran.dg/pr102332.f90: New test.