DOTImporter.setVertexWithAttributesFactory gets called with an empty string

[asarkar]

 * JGraphT version: 1.5.1
 * Java version (java -version)/platform:  11

I apologize if this issue has been raised before but I didn't find anything similar from Google search or by searching the issues in this repo.

Issue
Given the following graph:

strict digraph G {
  root="commons/master";
  "auth/master" [ comments="{\"ancestors\":[\"commons/master\",\"subscription/master\"]}" ];
  "commons/master" [ comments="{\"ancestors\":[]}" ];
  "subscription/master" [ comments="{\"ancestors\":[\"commons/master\"]}" ];
  "gateway/master" [ comments="{\"ancestors\":[\"auth/master\",\"commons/master\",\"subscription/master\"]}" ];
  "datetime/master" [ comments="{\"ancestors\":[\"commons/master\",\"subscription/master\"]}" ];
  "browse/master" [ comments="{\"ancestors\":[\"commons/master\"]}" ];
  "subscription/master" -> "auth/master";
  "commons/master" -> "subscription/master";
  "auth/master" -> "gateway/master";
  "subscription/master" -> "datetime/master";
  "commons/master" -> "browse/master";
}

DOTImporter.setVertexWithAttributesFactory gets called with an empty string for vertex, and no attributes. There is no way for the client to create a vertex from an empty string and returning null causes an NPE.

Expected behaviour
DOTImporter.setVertexWithAttributesFactory should not get called with an empty string for vertex.

Other information
FWIW, client code is in Kotlin.

[asarkar]

Looks like this happens when regular parsing fails due to a code bug. Parsing vertex "auth/master" was throwing an exception, and that caused the vertexWithAttributesFactory to be called with an empty string.