Don't panic on zero-length token from misformed subject

sublist/sublist.go

@@ -290,7 +290,7 @@ func (s *Sublist) Remove(subject []byte, sub interface{}) {
 	levels := lnts[:0]
 
 	for _, t := range toks {
-		if l == nil {
+		if l == nil || len(t) == 0 {
 			s.mu.Unlock()
 			return
 		}

sublist/sublist_test.go

@@ -357,6 +357,15 @@ func TestResultSetSnapshots(t *testing.T) {
 	verifyLen(r, 1, t)
 }
 
+func TestBadSubjectOnRemove(t *testing.T) {
+	bad := []byte("a.b..d")
+	value := "bad"
+
+	s := New()
+	s.Insert(bad, value)
+	s.Remove(bad, value)
+}
+
 // -- Benchmarks Setup --
 
 var subs [][]byte