inventory slots fix

src/frontend/InventoryView.cpp

@@ -296,6 +296,10 @@ void SlotView::clicked(gui::GUI* gui, int button) {
     }
 }
 
+void SlotView::focus(gui::GUI* gui) {
+    clicked(gui, 0);
+}
+
 InventoryView::InventoryView(
             const Content* content,
             LevelFrontend* frontend,

src/frontend/InventoryView.h

@@ -108,6 +108,7 @@ public:
     bool isHighlighted() const;
 
     virtual void clicked(gui::GUI*, int) override;
+    virtual void focus(gui::GUI*) override;
 };
 
 class InventoryView : public gui::Container {