Raise error in case dereference is performed on a scalar value.

Zend/zend_execute.c

@@ -1949,6 +1949,10 @@ int zend_fetch_dim_unset_handler(ZEND_OPCODE_HANDLER_ARGS)
 	if (EX_T(EX(opline)->result.u.var).EA.type == IS_STRING_OFFSET) {
 		zend_error(E_ERROR, "Cannot unset string offsets");
 	} else {
+		if (Z_TYPE_PP(EX_T(EX(opline)->result.u.var).var.ptr_ptr) != IS_ARRAY) {
+			zend_error(E_ERROR, "Illegal scalar dereference");
+		}
+
 		PZVAL_UNLOCK(*EX_T(EX(opline)->result.u.var).var.ptr_ptr);
 		if (EX_T(EX(opline)->result.u.var).var.ptr_ptr != &EG(uninitialized_zval_ptr)) {
 			SEPARATE_ZVAL_IF_NOT_REF(EX_T(EX(opline)->result.u.var).var.ptr_ptr);