Fix chat console not opening after formspec opened over it

The MainMenuManager set the console invisible when a
formspec opened over it, but didn't properly close it,
and the chat console never set itself visible again.

src/guiChatConsole.h

@@ -77,6 +77,8 @@ public:
 
 	virtual bool OnEvent(const SEvent& event);
 
+	virtual void setVisible(bool visible);
+
 private:
 	void reformatConsole();
 	void recalculateConsolePosition();