8308408: Build failure with -Werror=maybe-uninitialized in libjli/java.c with GCC8

Reviewed-by: alanb

Author: DamonFool

src/java.base/share/native/libjli/java.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1995, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1995, 2023, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -1205,7 +1205,7 @@ ParseArguments(int *pargc, char ***pargv,
     int argc = *pargc;
     char **argv = *pargv;
     int mode = LM_UNKNOWN;
-    char *arg;
+    char *arg = NULL;
 
     *pret = 0;