[Committed] PR fortran/88357 -- NULL pointer dereferences

[Steve Kargl]

Invalid code can cause the gfortran to dereference NULL pointers.
The patch fixes this.

2018-12-08 Steven G. Kargl <***@gcc.gnu.org>

PR fortran/88357
* class.c (insert_component_ref): Check for NULL pointer and
previous error message issued.
* parse.c (parse_associate): Check for NULL pointer.
* resolve.c (resolve_assoc_var): Check for NULL pointer.

2018-12-08 Steven G. Kargl <***@gcc.gnu.org>

* gfortran.dg/pr88357_1.f90: New test.
* gfortran.dg/pr88357_2.f90: New test.