fix leaking the empty_string in TS builds

Zend/zend.c

@@ -477,7 +477,10 @@ static void compiler_globals_dtor(zend_compiler_globals *compiler_globals TSRMLS
 	compiler_globals->last_static_member = 0;
 
 #ifdef ZTS
-	zend_string_release(compiler_globals->empty_string);
+	if (NULL != compiler_globals->empty_string) {
+		free(compiler_globals->empty_string);
+		compiler_globals->empty_string = NULL;
+	}
 #endif
 }
 /* }}} */

Zend/zend_string.c

@@ -80,7 +80,10 @@ void zend_interned_strings_dtor(TSRMLS_D)
 #ifndef ZTS
 	zend_hash_destroy(&CG(interned_strings));
 #else
-	zend_string_release(CG(empty_string));
+	if (NULL != CG(empty_string)) {
+		free(CG(empty_string));
+		CG(empty_string) = NULL;
+	}
 #endif
 }