MFB: fix #41813 (segmentation fault when using string offset as an object)

patch by judas dot iscariote at gmail dot com

Zend/zend_execute.c

@@ -552,6 +552,10 @@ static inline void zend_assign_to_object(znode *result, zval **object_ptr, znode
 	zval *value = get_zval_ptr(value_op, Ts, &free_value, BP_VAR_R);
 	zval **retval = &T(result->u.var).var.ptr;
 
+	if (!object_ptr) {
+		zend_error_noreturn(E_ERROR, "Cannot use string offset as an array");
+	}
+
 	if (*object_ptr == EG(error_zval_ptr)) {
 		FREE_OP(free_op2);
 		if (!RETURN_VALUE_UNUSED(result)) {