anticipate failure from add_np_edges

Related to #1801.

diff --git a/lib/ortho/ortho.c b/lib/ortho/ortho.c
index 7e00216caa21771e3bf14785a8c3315042f73de7..ffb43e45a1d90fcf31e748fce72359162d6b0e7f 100644 (file)
--- a/lib/ortho/ortho.c
+++ b/lib/ortho/ortho.c
@@ -1082,8 +1082,12 @@ assignTracks (maze* mp)
     create_graphs(mp->vchans);
 
     /* add edges between non-parallel segments */
-    add_np_edges(mp->hchans);
-    add_np_edges(mp->vchans);
+    if (add_np_edges(mp->hchans) != 0) {
+       return -1;
+    }
+    if (add_np_edges(mp->vchans) != 0) {
+       return -1;
+    }
 
     /* add edges between parallel segments + remove appropriate edges */
     add_p_edges(mp->hchans, mp);