re PR fortran/50981 ([OOP] Wrong-code for scalarizing ELEMENTAL call with absent OPTIONAL argument)

	PR fortran/50981
	* trans.h (struct gfc_ss_info): New field data::scalar::can_be_null_ref
	* trans-array.c: If the reference can be NULL, save the reference
	instead of the value.
	* trans-expr.c (gfc_conv_expr): If we have saved a reference,
	dereference it.

From-SVN: r182874