appending text to a text node works even when the node is hidden

hide the gui with "h", have the mouse over a text node and type something
this **blocks** normal hotkeys like "h" for showing the gui and instead appends "h" to the text, 
but you can't even see the text node at that point, so that's not expected behavior

we need to check if the node is visible before letting the keyboard interact with the text node