.

wcfs/internal/zdata/δftail.go

@@ -471,10 +471,14 @@ func (δFtail *ΔFtail) Update(δZ *zodb.EventCommit) (_ ΔF, err error) {
 	//fmt.Printf("δB.ByRoot: %v\n", δB.ByRoot)
 	for root, δt := range δB.ByRoot {
 		//fmt.Printf("root: %v   δt: %v\n", root, δt)
-		rt := δFtail.byRoot[root] // XXX root must be tracked, right?
-		// NOTE files might be empty e.g. if a zfile was tracked, then
+		rt, ok := δFtail.byRoot[root]
+		// NOTE rt might be nil e.g. if a zfile was tracked, then
 		// deleted, but the tree referenced by zfile.blktab is still
 		// not-deleted, remains tracked and is changed.
+		if !ok {
+			continue
+		}
+
 		for file := range rt.files {
 			δfile, ok := δF.ByFile[file]
 			if !ok {
@@ -555,7 +559,7 @@ func (δFtail *ΔFtail) Update(δZ *zodb.EventCommit) (_ ΔF, err error) {
 
 		//fmt.Printf("δZBigFile: %v\n", δ)
 
-		// update .filesByRoot
+		// update .byRoot
 		if δ.blktabOld != xbtree.VDEL {
 			rt, ok := δFtail.byRoot[δ.blktabOld]
 			if ok {