Fixed tile replacement to add tileset when needed (#1641)

Make sure tileset is added to the map when replacing a tile of an object.

src/tiled/changemapobject.cpp

@@ -118,6 +118,18 @@ static void setObjectCell(MapObject *object,
         object->setSize(cell.tile()->size());
 }
 
+void ChangeMapObjectsTile::undo()
+{
+    restoreTiles();
+    QUndoCommand::undo(); // undo child commands
+}
+
+void ChangeMapObjectsTile::redo()
+{
+    QUndoCommand::redo(); // redo child commands
+    changeTiles();
+}
+
 void ChangeMapObjectsTile::restoreTiles()
 {
     for (int i = 0; i < mMapObjects.size(); ++i)

src/tiled/changemapobject.h

@@ -94,8 +94,8 @@ class ChangeMapObjectsTile : public QUndoCommand
                          const QList<MapObject *> &mapObjects,
                          Tile *tile);
 
-    void undo() override { restoreTiles(); }
-    void redo() override { changeTiles(); }
+    void undo() override;
+    void redo() override;
 
 private:
     void changeTiles();

src/tiled/tilesetdock.cpp

@@ -1006,6 +1006,12 @@ void TilesetDock::changeSelectedMapObjectsTile(Tile *tile)
     if (tileObjects.isEmpty())
         return;
 
-    QUndoStack *undoStack = mMapDocument->undoStack();
-    undoStack->push(new ChangeMapObjectsTile(mMapDocument, tileObjects, tile));
+    auto changeMapObjectCommand = new ChangeMapObjectsTile(mMapDocument, tileObjects, tile);
+
+    // Make sure the tileset is part of the map
+    SharedTileset sharedTileset = tile->tileset()->sharedPointer();
+    if (!mMapDocument->map()->tilesets().contains(sharedTileset))
+        new AddTileset(mMapDocument, sharedTileset, changeMapObjectCommand);
+
+    mMapDocument->undoStack()->push(changeMapObjectCommand);
 }