actions: toggle screen lock: check if screen is lockable before asking for width

src/lyrics.h

@@ -45,6 +45,7 @@ struct Lyrics: Screen<NC::Scrollpad>, Tabbable
 	virtual void enterPressed() OVERRIDE { }
 	virtual void spacePressed() OVERRIDE;
 	
+	virtual bool isLockable() OVERRIDE { return false; }
 	virtual bool isMergable() OVERRIDE { return true; }
 	
 	// private members
@@ -60,9 +61,6 @@ struct Lyrics: Screen<NC::Scrollpad>, Tabbable
 	
 	bool Reload;
 	
-protected:
-	virtual bool isLockable() OVERRIDE { return false; }
-	
 private:
 	void Load();