Fail safely on invalid ScanResults when creating NetworkKey

Added tests for NetworkKey#createFromScanResult

Bug: 34671341
Test: runtest --path
frameworks/base/core/tests/coretests/src/android/net/NetworkKeyTest.java
runtest --path
frameworks/base/services/tests/servicestests/src/com/android/server/NetworkScoreServiceTest.java

Change-Id: Ideac1615917649cd3934421228a82aeed37e7ad1
diff --git a/services/core/java/com/android/server/NetworkScoreService.java b/services/core/java/com/android/server/NetworkScoreService.java
index 3e89852..b33538cb 100644
--- a/services/core/java/com/android/server/NetworkScoreService.java
+++ b/services/core/java/com/android/server/NetworkScoreService.java
@@ -603,7 +603,10 @@
             mScanResultKeys = new ArraySet<>(size);
             for (int i = 0; i < size; i++) {
                 ScanResult scanResult = scanResults.get(i);
-                mScanResultKeys.add(NetworkKey.createFromScanResult(scanResult));
+                NetworkKey key = NetworkKey.createFromScanResult(scanResult);
+                if (key != null) {
+                    mScanResultKeys.add(key);
+                }
             }
         }