1.1 --- a/src/lemon/graph_writer.h	Tue Apr 12 17:33:41 2005 +0000
     1.2 +++ b/src/lemon/graph_writer.h	Tue Apr 12 17:34:51 2005 +0000
     1.3 @@ -382,6 +382,7 @@
     1.4  
     1.5      void writeEdgeSet(WriterBase<Node>* nodeWriter, 
     1.6  		      WriterBase<Edge>* & edgeWriter) {
     1.7 +      if (edge_map_writers.size() == 0) return;
     1.8        if (nodeWriter == 0) {
     1.9  	throw DataFormatError("Cannot find node id map");
    1.10        }
    1.11 @@ -406,6 +407,7 @@
    1.12      }
    1.13  
    1.14      void writeNodes(WriterBase<Node>* nodeWriter) {
    1.15 +      if (node_writers.size() == 0) return;
    1.16        if (nodeWriter == 0) {
    1.17  	throw DataFormatError("Cannot find node id map");
    1.18        }
    1.19 @@ -418,6 +420,7 @@
    1.20      }
    1.21  
    1.22      void writeEdges(WriterBase<Edge>* edgeWriter) {
    1.23 +      if (edge_writers.size() == 0) return;
    1.24        if (edgeWriter == 0) {
    1.25  	throw DataFormatError("Cannot find node id map");
    1.26        }