delete the empty folder itself too

app/src/main/java/com/simplemobiletools/gallery/activities/MainActivity.java

@@ -173,10 +173,13 @@ public class MainActivity extends AppCompatActivity
                 updatedFiles.add(f.getAbsolutePath());
                 f.delete();
             }
+            updatedFiles.add(dir.getAbsolutePath());
+            dir.delete();
         }
 
         final String[] deletedPaths = updatedFiles.toArray(new String[updatedFiles.size()]);
         MediaScannerConnection.scanFile(this, deletedPaths, null, null);
+        toBeDeleted.clear();
     }
 
     private View.OnClickListener undoDeletion = new View.OnClickListener() {

app/src/main/java/com/simplemobiletools/gallery/activities/PhotosActivity.java

@@ -194,6 +194,7 @@ public class PhotosActivity extends AppCompatActivity
 
         final String[] deletedPaths = toBeDeleted.toArray(new String[toBeDeleted.size()]);
         MediaScannerConnection.scanFile(this, deletedPaths, null, this);
+        toBeDeleted.clear();
     }
 
     private View.OnClickListener undoDeletion = new View.OnClickListener() {

app/src/main/java/com/simplemobiletools/gallery/activities/ViewPagerActivity.java

@@ -143,6 +143,7 @@ public class ViewPagerActivity extends AppCompatActivity
             final String[] deletedPath = new String[]{toBeDeleted};
             MediaScannerConnection.scanFile(this, deletedPath, null, this);
         }
+        toBeDeleted = "";
     }
 
     private View.OnClickListener undoDeletion = new View.OnClickListener() {