Manage missing trajectories

This can happen if the input graph file contains only an extracted
component.

Trajectories/draw_segments.py

@@ -49,9 +49,13 @@ if args.t:
         color = next(colors)
 
         for segment in segment_list:
-            n = g_out.get_node(segment)
-            n.attr["label"] = f"{segment} in {i}"
-            n.attr["color"] = color
+            try:
+                n = g_out.get_node(segment)
+            except KeyError:
+                break
+            else:
+                n.attr["label"] = f"{segment} in {i}"
+                n.attr["color"] = color
 
 g_out.write(args.output_file)