Add nonnull annotation

src/org/kde/kdeconnect/Helpers/SMSHelper.java

@@ -40,6 +40,7 @@ import java.util.concurrent.locks.Condition;
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 
+import androidx.annotation.NonNull;
 import androidx.annotation.RequiresApi;
 
 public class SMSHelper {
@@ -221,6 +222,7 @@ public class SMSHelper {
             this.threadID = threadID;
         }
 
+        @NonNull
         public String toString() {
             return this.threadID.toString();
         }

src/org/kde/kdeconnect/Plugins/SystemvolumePlugin/SystemvolumeFragment.java

@@ -46,7 +46,7 @@ public class SystemvolumeFragment extends ListFragment implements Sink.UpdateLis
     private boolean tracking;
 
     @Override
-    public void onViewCreated(View view, Bundle savedInstanceState) {
+    public void onViewCreated(@NonNull View view, Bundle savedInstanceState) {
         super.onViewCreated(view, savedInstanceState);
         getListView().setDivider(null);
         setListAdapter(new SinkAdapter(getContext(), new Sink[0]));