[android] Clean up a couple of unnecessary test runner log warnings.

build/android/pylib/instrumentation/instrumentation_test_instance.py

Index: build/android/pylib/instrumentation/instrumentation_test_instance.py
diff --git a/build/android/pylib/instrumentation/instrumentation_test_instance.py b/build/android/pylib/instrumentation/instrumentation_test_instance.py
index d01e36eeeee8a84eba18096a487f0a75eb4ac678..d8f0995269327ff03c4407424f3b5c37fb86d0a1 100644
--- a/build/android/pylib/instrumentation/instrumentation_test_instance.py
+++ b/build/android/pylib/instrumentation/instrumentation_test_instance.py
@@ -685,7 +685,7 @@ class InstrumentationTestInstance(test_instance.TestInstance):
     self._should_save_logcat = bool(args.json_results_file)
 
   def _initializeEditPrefsAttributes(self, args):
-    if not hasattr(args, 'shared_prefs_file'):
+    if not hasattr(args, 'shared_prefs_file') or not args.shared_prefs_file:
       return
     if not isinstance(args.shared_prefs_file, str):
       logging.warning("Given non-string for a filepath")