bug#21548: 25.0.50; [PATCH] Prevent empty -path arguments for not-ignored directories in rgrep's find commands

[Eli Zaretskii]

> Date: Thu, 24 Sep 2015 23:28:39 +1200
> From: Phil Sainty <psainty@orcon.net.nz>
> 
> rgrep's `grep-find-ignored-directories' conditional-ignore behaviour
> (for list elements which are cons cells) produces 'find' constraints
> like: "find . -type d \( -path  -o -path \*/SCCS [...]" (i.e. a -path
> argument with no value) when the associated function returns nil.
> 
> The nil elements need to be deleted from the list before the command
> line arguments for the ignored directories are generated.

Thanks, I pushed this.

Please in the future accompany your patches with a ChangeLog-format
commit message; see CONTRIBUTE for details.

We seem to lack tests for this stuff (and Grep in general).  Would you
like to write some tests for that?  TIA.