re PR tree-optimization/71239 (ICE in operand_equal_p (fold-const.c:2769))

Fix PR tree-optimization/71239.

	* g++.dg/pr71239.C: New test.
	PR tree-optimization/71239
	* tree.c (array_at_struct_end_p): Do not call operand_equal_p
	if DECL_SIZE is NULL.

From-SVN: r236696