adding a crashfix

app/src/main/kotlin/com/simplemobiletools/musicplayer/dialogs/ChangeSortingDialog.kt

@@ -141,7 +141,9 @@ class ChangeSortingDialog(val activity: Activity, val location: Int, val playlis
                     if (view.sorting_dialog_use_for_this_playlist.isChecked) {
                         config.saveCustomPlaylistSorting(playlist!!.id, sorting)
                     } else {
-                        config.removeCustomPlaylistSorting(playlist!!.id)
+                        if (playlist != null) {
+                            config.removeCustomPlaylistSorting(playlist.id)
+                        }
                         config.playlistTracksSorting = sorting
                     }
                 }

app/src/main/res/layout/dialog_change_sorting.xml

@@ -54,6 +54,7 @@
             android:id="@+id/sorting_dialog_use_for_this_playlist"
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
+            android:checked="false"
             android:paddingTop="@dimen/activity_margin"
             android:paddingBottom="@dimen/activity_margin"
             android:text="@string/use_for_this_playlist" />