Fortran: Prevent ICE when getting caf-token from abstract type [PR77872]

	PR fortran/77872

gcc/fortran/ChangeLog:

	* trans-expr.cc (gfc_get_tree_for_caf_expr): Pick up token from
	decl when it is present there for class types.

gcc/testsuite/ChangeLog:

	* gfortran.dg/coarray/class_1.f90: New test.