8e3f3a01dbb1b2ac9d3c7fed4fb2840dcb6014f6
braney
  Sat Sep 28 10:09:20 2019 -0700
allow trackDb variables to have an empty value, useful for filters

diff --git src/hg/lib/trackDbCustom.c src/hg/lib/trackDbCustom.c
index 7a63807..f68a3c3 100644
--- src/hg/lib/trackDbCustom.c
+++ src/hg/lib/trackDbCustom.c
@@ -349,31 +349,31 @@
         {
         /* Break at blank line or EOF. */
         if (!lineFileNextFull(lf, &line, NULL, NULL, NULL))  // NOTE: joins continuation lines
             break;
         line = skipLeadingSpaces(line);
         if (line == NULL || line[0] == 0)
             break;
 
         /* Skip comments. */
         if (line[0] == '#')
             continue;
 
         /* Parse out first word and decide what to do. */
         word = nextWord(&line);
         if (line == NULL)
-            errAbort("No value for %s line %d of %s", word, lf->lineIx, lf->fileName);
+            line = "";
         line = trimSpaces(line);
         trackDbUpdateOldTag(&word, &line);
         if (releaseTag && sameString(word, "release"))
             {
             if (differentString(releaseTag, line))
                 errAbort("Release tag %s in stanza with include override %s, line %d of %s",
                     line, releaseTag, lf->lineIx, lf->fileName);
             }
         else
             trackDbAddInfo(bt, word, line, lf);
         }
     if (releaseTag)
         trackDbAddRelease(bt, releaseTag);
     }
 slReverse(&btList);