d3f9b9ecf2a6d30bd8f97566f72e5650982c308d
kent
  Mon Dec 13 15:22:03 2021 -0800
Adding hgTracks display of merged bar charts.

diff --git src/hg/lib/facetField.c src/hg/lib/facetField.c
index 7fe57d3..8e44dc3 100644
--- src/hg/lib/facetField.c
+++ src/hg/lib/facetField.c
@@ -256,30 +256,31 @@
     }
 else if (sameString(op, "merge"))
     {
     sff->isMerged = TRUE;
     }
 else if (sameString(op, "unmerge"))
     {
     sff->isMerged = FALSE;
     }
 *pSelectedList = selectedList;
 }
 
 struct facetField *deLinearizeFacetValString(char *selectedFields)
 /* Turn linearized selected fields string back into facet structures */
 {
+if (selectedFields == NULL) return NULL;  // Empty input means empty output
 struct facetField *ffList = NULL, *ff;
 boolean done = FALSE;
 while (!done)
     {
     if (sameString(selectedFields, ""))
 	break;
     char *end = strchr(selectedFields, facetValStringPunc);
     if (!end)
 	{
 	end = selectedFields + strlen(selectedFields);
 	done = TRUE;
 	}
     char saveEnd = *end;
     *end = 0;
     char *spc = strchr(selectedFields, ' ');