Guard against exception when reg/unreg content observer

When an app injects an entry to Settings with dynamic title/summary, and
disables its content provider at runtime, Settings will crash while
trying to registering/unregistering the data observer.

Fix: 337567627
Test: manual
Flag: EXEMPT bugfix
Change-Id: I9c7f689c6696d91f0b8e40113a8df10375930ede

src/com/android/settings/dashboard/DashboardFragment.java

@@ -649,8 +649,12 @@ public abstract class DashboardFragment extends SettingsPreferenceFragment
             DynamicDataObserver observer) {
         Log.d(TAG, "register observer: @" + Integer.toHexString(observer.hashCode())
                 + ", uri: " + observer.getUri());
+        try {
             resolver.registerContentObserver(observer.getUri(), false, observer);
             mRegisteredObservers.add(observer);
+        } catch (Exception e) {
+            Log.w(TAG, "Cannot register observer: " + observer.getUri(), e);
+        }
     }
 
     private void unregisterDynamicDataObservers(List<DynamicDataObserver> observers) {
@@ -661,8 +665,13 @@ public abstract class DashboardFragment extends SettingsPreferenceFragment
         observers.forEach(observer -> {
             Log.d(TAG, "unregister observer: @" + Integer.toHexString(observer.hashCode())
                     + ", uri: " + observer.getUri());
-            mRegisteredObservers.remove(observer);
+            if (mRegisteredObservers.remove(observer)) {
+                try {
                     resolver.unregisterContentObserver(observer);
+                } catch (Exception e) {
+                    Log.w(TAG, "Cannot unregister observer: " + observer.getUri(), e);
+                }
+            }
         });
     }