bug#48408: BUGFIX: window-default-font-height: check for nil string

[martin rudalics]

> 1) In working on this bug, I noticed that the mode line on the GUI frame
>     was not correctly indicating the frame name.

What do you use to indicate the frame name in the mode line?  If you
have a title bar, does it correctly display the frame name?  Note also
that "the" mode line is ambiguous - with split windows a frame usually
has several mode lines.

>     2.1) Whenever a minibuffer is active in one frame, the other windows
>          on that frame are navigable and operable. However, all elements
>          of all other frames are completely frozen.

What happens when you type C-x 5 o or C-x 5 2 in the navigable frame?

martin