8217563: Improve realm maintenance

Reviewed-by: mullan, mschoene, valeriep

src/macosx/native/java/util/SCDynamicStoreConfig.m

 /*
- * Copyright (c) 2011, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2011, 2019, 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
@@ -102,7 +102,8 @@ NSDictionary *realmConfigsForRealms(SCDynamicStoreRef store, NSArray *realms) {
     for (NSString *realm in realms) {
         CFTypeRef realmInfo = SCDynamicStoreCopyValue(store, (CFStringRef) [NSString stringWithFormat:@"Kerberos:%@", realm]);
 
-        if (CFGetTypeID(realmInfo) != CFDictionaryGetTypeID()) {
+        if (realmInfo == NULL || CFGetTypeID(realmInfo) != CFDictionaryGetTypeID()) {
+            if (realmInfo) CFRelease(realmInfo);
             return nil;
         }