fold-const: Fix up fold_truth_andor_1 shift handling [PR103813]

Some time ago I've changed const_binop -> wide_int_binop, so that it punts
on shifts by negative count.  fold_truth_andor_1 doesn't check the results
of const_binop (?SHIFT_EXPR, ) though and assumes they will be always
non-NULL, which is no longer the case.

2021-12-28  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/103813
	* fold-const.c (fold_truth_andor_1): Punt of const_binop LSHIFT_EXPR
	or RSHIFT_EXPR returns NULL.  Formatting fix.

	* gcc.c-torture/compile/pr103813.c: New test.