Gnss:fix NPE due to the arraymap store the null key.

 PersistableBundle store the data use the ArrayMap,so the null key may put into the map.So we should make a judgment to prevent the systemserver crash.

Bug: 337781283
Change-Id: I9ce8c86aa9c9142e3b413bdb1eaaf51099592e72

services/core/java/com/android/server/location/gnss/GnssConfiguration.java

@@ -379,7 +379,7 @@ public class GnssConfiguration {
             configs = CarrierConfigManager.getDefaultConfig();
         }
         for (String configKey : configs.keySet()) {
-            if (configKey.startsWith(CarrierConfigManager.Gps.KEY_PREFIX)) {
+            if (configKey != null && configKey.startsWith(CarrierConfigManager.Gps.KEY_PREFIX)) {
                 String key = configKey
                         .substring(CarrierConfigManager.Gps.KEY_PREFIX.length())
                         .toUpperCase();