fix: pr review comments

Author: avinash-newrelic

NewRelicVideoCore/src/main/java/com/newrelic/videoagent/core/auth/TokenManager.java

@@ -164,7 +164,8 @@ private String buildTokenEndpoint() {
         }
 
         // Otherwise, auto-detect from region
-        String region = configuration.getRegion().toUpperCase();
+        String region = configuration.getRegion();
+        region = (region != null) ? region.toUpperCase() : "US";
         switch (region) {
             case "EU":
                 return "https://mobile-collector.eu.newrelic.com/mobile/v5/connect";

NewRelicVideoCore/src/main/java/com/newrelic/videoagent/core/harvest/OptimizedHttpClient.java

@@ -63,9 +63,9 @@ public OptimizedHttpClient(NRVideoConfiguration configuration, android.content.C
             this.endpointUrl = "https://" + configuration.getCollectorAddress() + "/mobile/v3/data";
         } else {
             // Otherwise, auto-detect from region
-            String region = configuration.getRegion().toUpperCase();
-            String regionEndpoint = REGIONAL_ENDPOINTS.get(region);
-            this.endpointUrl = regionEndpoint != null ? regionEndpoint : REGIONAL_ENDPOINTS.get("DEFAULT");
+            String region = configuration.getRegion();
+            region = (region != null) ? region.toUpperCase() : "US";
+            this.endpointUrl = REGIONAL_ENDPOINTS.getOrDefault(region, REGIONAL_ENDPOINTS.get("DEFAULT"));
         }
 
         if (configuration.isMemoryOptimized()) {