Fix confusion by GCC in zend_inference

Author: Girgias

Zend/Optimizer/zend_inference.c

@@ -4634,6 +4634,9 @@ ZEND_API int zend_may_throw_ex(const zend_op *opline, const zend_ssa_op *ssa_op,
 					return 0;
 				EMPTY_SWITCH_DEFAULT_CASE()
 			}
+			/* GCC is getting confused here for the Wimplicit-fallthrough warning with
+			 * EMPTY_SWITCH_DEFAULT_CASE() macro */
+			return 0;
 		case ZEND_ARRAY_KEY_EXISTS:
 			if ((t2 & MAY_BE_ANY) != MAY_BE_ARRAY) {
 				return 1;