fix a bunch of lint warnings

app/src/main/java/com/dkanada/gramophone/dialogs/AddToPlaylistDialog.java

@@ -8,7 +8,6 @@ import androidx.fragment.app.DialogFragment;
 
 import com.afollestad.materialdialogs.MaterialDialog;
 import com.dkanada.gramophone.R;
-import com.dkanada.gramophone.interfaces.MediaCallback;
 import com.dkanada.gramophone.model.Playlist;
 import com.dkanada.gramophone.model.Song;
 import com.dkanada.gramophone.util.PlaylistUtil;

app/src/main/java/com/dkanada/gramophone/dialogs/CreatePlaylistDialog.java

@@ -58,4 +58,4 @@ public class CreatePlaylistDialog extends DialogFragment {
                 })
                 .build();
     }
-}
+}

app/src/main/java/com/dkanada/gramophone/dialogs/DeletePlaylistDialog.java

@@ -40,7 +40,6 @@ public class DeletePlaylistDialog extends DialogFragment {
         final List<Playlist> playlists = getArguments().getParcelableArrayList("playlists");
         int title;
         CharSequence content;
-        // noinspection ConstantConditions
         if (playlists.size() > 1) {
             title = R.string.delete_playlists_title;
             content = Html.fromHtml(getString(R.string.delete_x_playlists, playlists.size()));

app/src/main/java/com/dkanada/gramophone/dialogs/RenamePlaylistDialog.java

@@ -29,7 +29,7 @@ public class RenamePlaylistDialog extends DialogFragment {
     @NonNull
     @Override
     public Dialog onCreateDialog(Bundle savedInstanceState) {
-        return new MaterialDialog.Builder(requireContext())
+        return new MaterialDialog.Builder(requireActivity())
             .title(R.string.rename_playlist_title)
             .positiveText(R.string.rename_action)
             .negativeText(android.R.string.cancel)
@@ -44,4 +44,4 @@ public class RenamePlaylistDialog extends DialogFragment {
             })
             .build();
     }
-}
+}