81f1e4fa0106db9d0d049d739302cccc09e1dfcb
braney
  Thu Feb 6 10:21:46 2014 -0800
fix crash in multiWig if underlying bigWig file was not found
diff --git src/hg/hgTracks/multiWig.c src/hg/hgTracks/multiWig.c
index fa54dc4..1d89247 100644
--- src/hg/hgTracks/multiWig.c
+++ src/hg/hgTracks/multiWig.c
@@ -163,30 +163,33 @@
 freez(&lineBuf);
 }
 
 
 static void minMaxVals(struct slRef *refList, double *retMin, double *retMax,
      enum wiggleAlwaysZeroEnum alwaysZero)
 /* Figure out min/max of everything in list.  The refList contains pointers to
  * preDrawContainers */
 {
 /* Turns out to be *much* shorter to rewrite than to reuse preDrawAutoScale */
 double max = -BIGDOUBLE, min = BIGDOUBLE;
 struct slRef *ref;
 for (ref = refList; ref != NULL; ref = ref->next)
     {
     struct preDrawContainer *pre = ref->val;
+    if (pre == NULL)  // pre may be null if the bigWig file didn't load
+	continue;
+
     struct preDrawElement *p = pre->preDraw + pre->preDrawZero;
     int width = pre->width;
     int i;
     for (i=0; i<width; ++i)
 	{
 	if (p->count)
 	    {
 	    if (min > p->min) min = p->min;
 	    if (max < p->max) max = p->max;
 	    }
 	++p;
 	}
     }
 if (alwaysZero == wiggleAlwaysZeroOn)
     {