[Settings] Fix crash when user enter bluetooth page quickly.

- When SliceManager try to pinSlice, process may not have the permssion
   yet, so in Androix lib it use try/catch to avoid Security exception.
   However, if SliceManger quickly unpinSlice after pinSlice, process
   may still not get the permission yet, then due to no security
   exception, it cause the settings crash.

Bug: 283065718
Test: atest passed
Test: Manual test passed
Change-Id: I2293fca73e65dfaa34237abe57e0c6a3fe0f62bb

src/com/android/settings/bluetooth/BlockingPrefWithSliceController.java

@@ -113,15 +113,27 @@ public class BlockingPrefWithSliceController extends BasePreferenceController im
 
     @Override
     public void onStart() {
-        if (mLiveData != null) {
+        if (mLiveData == null) {
+            return;
+        }
+
+        try {
             mLiveData.observeForever(this);
+        } catch (SecurityException e) {
+            Log.w(TAG, "observeForever - no permission");
         }
     }
 
     @Override
     public void onStop() {
-        if (mLiveData != null) {
+        if (mLiveData == null) {
+            return;
+        }
+
+        try {
             mLiveData.removeObserver(this);
+        } catch (SecurityException e) {
+            Log.w(TAG, "removeObserver - no permission");
         }
     }
 

src/com/android/settings/slices/SlicePreferenceController.java

@@ -44,7 +44,6 @@ public class SlicePreferenceController extends BasePreferenceController implemen
     LiveData<Slice> mLiveData;
     @VisibleForTesting
     SlicePreference mSlicePreference;
-    private boolean mIsObservering = false;
     private Uri mUri;
 
     public SlicePreferenceController(Context context, String preferenceKey) {
@@ -74,9 +73,14 @@ public class SlicePreferenceController extends BasePreferenceController implemen
 
     @Override
     public void onStart() {
-        if (mLiveData != null && !mIsObservering) {
-            mIsObservering = true;
+        if (mLiveData == null) {
+            return;
+        }
+
+        try {
             mLiveData.observeForever(this);
+        } catch (SecurityException e) {
+            Log.w(TAG, "observeForever - no permission");
         }
     }
 
@@ -91,9 +95,14 @@ public class SlicePreferenceController extends BasePreferenceController implemen
     }
 
     private void removeLiveDataObserver() {
-        if (mLiveData != null && mIsObservering && mLiveData.hasActiveObservers()) {
-            mIsObservering = false;
+        if (mLiveData == null) {
+            return;
+        }
+
+        try {
             mLiveData.removeObserver(this);
+        } catch (SecurityException e) {
+            Log.w(TAG, "removeLiveDataObserver - no permission");
         }
     }
 }