completions/portage: Fix errors with unreadable files

This could occur if a non-readable location was mentioned in one of
the portage config files.

Fixes #9495

share/functions/__fish_print_portage_available_pkgs.fish

@@ -1,3 +1,6 @@
 function __fish_print_portage_available_pkgs --description 'Print all available packages'
-    find (__fish_print_portage_repository_paths) -mindepth 2 -maxdepth 2 -type d ! '(' '(' -path '*/eclass/*' -o -path '*/metadata/*' -o -path '*/profiles/*' -o -path '*/.*/*' ')' -prune ')' -printf '%P\n'
+    set -l paths (__fish_print_portage_repository_paths)
+    set -q paths[1]
+    or return
+    find $paths -mindepth 2 -maxdepth 2 -type d ! '(' '(' -path '*/eclass/*' -o -path '*/metadata/*' -o -path '*/profiles/*' -o -path '*/.*/*' ')' -prune ')' -printf '%P\n' 2>/dev/null
 end

share/functions/__fish_print_portage_installed_pkgs.fish

@@ -1,3 +1,3 @@
 function __fish_print_portage_installed_pkgs --description 'Print all installed packages (non-deduplicated)'
-    find /var/db/pkg -mindepth 2 -maxdepth 2 -type d -printf '%P\n' | string replace -r -- '-[0-9][0-9.]*.*$' ''
+    find /var/db/pkg -mindepth 2 -maxdepth 2 -type d -printf '%P\n' 2>/dev/null | string replace -r -- '-[0-9][0-9.]*.*$' ''
 end

share/functions/__fish_print_portage_repository_paths.fish

@@ -3,12 +3,14 @@ function __fish_print_portage_repository_paths --description 'Print the paths of
     set -l b
     set -l c /usr/share/portage/config/repos.conf
     test -d $a
-    and set b (find $a -type f )
+    and set b (find $a -type f 2>/dev/null)
     test -f $a
     and set b $a
     test -n "$b"
-    and string match -q "[gentoo]" -- (cat $b)
+    and string match -q "[gentoo]" -- (cat $b 2>/dev/null)
     and set c $b
     or set -a c $b
-    cat $c | string match -g -r '^location = (.*$)'
+    path is -r -- $c
+    or return
+    cat $c 2>/dev/null | string match -g -r '^location = (.*$)'
 end