GUI: Fix mobile controls

platforms/sdl/base/AppPlatform_sdl_base.hpp

@@ -38,8 +38,14 @@ public:
 	// Also add these to allow proper text input within the game.
 	bool shiftPressed() override;
 	void setShiftPressed(bool b, bool isLeft);
-	
-	bool isTouchscreen() override { return false; }
+
+	bool isTouchscreen() override {
+#ifdef MOBILE
+		return true;
+#else
+		return false;
+#endif
+	}
 
 	static MouseButtonType GetMouseButtonType(SDL_Event event);
 	static bool GetMouseButtonState(SDL_Event event);