Check ManagedResource is NonNull before Checking Owner

If an invalid Resource Id is provided to the Managed Resource
Array getter, we should just return null rather than asserting
the owner of the resource.

Bug: none
Test: tbd
Change-Id: I407a96e4e82e9d6bf68e89380a88d3851efe4305

services/core/java/com/android/server/IpSecService.java

@@ -206,7 +206,11 @@ public class IpSecService extends IIpSecService.Stub {
 
         T get(int key) {
             T val = mArray.get(key);
+            // The value should never be null unless the resource doesn't exist
+            // (since we do not allow null resources to be added).
+            if (val != null) {
                 val.checkOwnerOrSystemAndThrow();
+            }
             return val;
         }