Fix the invalid expr syntax in the m command.

[duck57]

This patch would also fix the corresponding line in budspencer.

In ~/.config/fish/function/fish_prompt.fish line 301 or thereabout, there is a line

set input_length (expr length (expr $num_items - 1))

In more recent versions of fish, this causes an error that then affects the following line. It can be changed to

set input_length (string length (expr $num_items - 1))

as a fix.

However, this still does not have the behavior of clearing the marked items after the directory selection is made.

[duck57]

FYI, I think there was some update to fish itself that broke this. The same file works just fine under 3.1.2; it was fish 3.4.1 that was giving me trouble.