Fix the test breakage. Do not assert on SrcUIDs being nil, instead re…

…turn an error.

query/query.go

@@ -1909,7 +1909,11 @@ func ProcessGraph(ctx context.Context, sg, parent *SubGraph, rch chan error) {
 			return
 		}
 
-		x.AssertTruef(sg.SrcUIDs != nil, "SrcUIDs shouldn't be nil.")
+		if sg.SrcUIDs == nil {
+			glog.Errorf("SrcUIDs is unexpectedly nil. Subgraph: %+v", sg)
+			rch <- x.Errorf("SrcUIDs shouldn't be nil.")
+			return
+		}
 		// If we have a filter SubGraph which only contains an operator,
 		// it won't have any attribute to work on.
 		// This is to allow providing SrcUIDs to the filter children.

raftwal/storage.go

@@ -341,6 +341,8 @@ func (w *DiskStorage) setHardState(batch *badger.WriteBatch, st pb.HardState) er
 
 // reset resets the entries. Used for testing.
 func (w *DiskStorage) reset(es []pb.Entry) error {
+	w.cache = new(sync.Map) // reset cache.
+
 	// Clean out the state.
 	batch := w.db.NewWriteBatch()
 	defer batch.Cancel()