[yelp-tools] yelp-build: Don't spit out error about missing stack files

[Shaun McCance <shaunm src gnome org>]

commit 794feea447da856d32d10fd74582b0af86a887d1
Author: Shaun McCance <shaunm gnome org>
Date:   Sun Jan 13 18:06:06 2019 -0500

    yelp-build: Don't spit out error about missing stack files
    
    Bare sh doesn't have nullglob, so we have to check the existence of
    filenames we got from iterating over a glob.

 tools/yelp-build.in | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/tools/yelp-build.in b/tools/yelp-build.in
index 447eda9..8438a23 100755
--- a/tools/yelp-build.in
+++ b/tools/yelp-build.in
@@ -195,7 +195,9 @@ yelp_cache_in () {
                 yelp_cache_in_site "$page"
             else
                 for sub in "$page"/*.page "$page"/*.stack; do
-                    yelp_cache_in_page "$sub"
+                    if [ -e "$page" ]; then
+                        yelp_cache_in_page "$sub"
+                    fi
                 done
             fi
         else