Fix null pointer on dismissing suggestion.

Add null check for context when getting the suggestion identifier, since
this is called from async task and context might becomes null.

Change-Id: If17036803de1634891b659a4fc6bd4b8a76ef5fb
Fix: 36605386
Test: make RunSettingsRoboTests

src/com/android/settings/dashboard/suggestions/SuggestionFeatureProviderImpl.java

@@ -83,7 +83,8 @@ public class SuggestionFeatureProviderImpl implements SuggestionFeatureProvider
 
     @Override
     public String getSuggestionIdentifier(Context context, Tile suggestion) {
-        if (suggestion.intent == null || suggestion.intent.getComponent() == null) {
+        if (suggestion.intent == null || suggestion.intent.getComponent() == null
+                || context == null) {
             return "unknown_suggestion";
         }
         String packageName = suggestion.intent.getComponent().getPackageName();