NumberFormatException on opening a project

[Mathieu Bastian]

Project file compatibility has been broken on 0.7alpha2 due to a bug. Files saved with 0.7alpha throw errors when opened with current version.

Stack trace:

java.lang.NumberFormatException: For input string: \"\"
 at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
 at java.lang.Integer.parseInt(Integer.java:470)
 at java.lang.Integer.parseInt(Integer.java:499)
 at org.gephi.graph.dhns.utils.DHNSSerializer.readTreeStructure(DHNSSerializer.java:229)
 at org.gephi.graph.dhns.utils.DHNSSerializer.readDhns(DHNSSerializer.java:136)
 at org.gephi.graph.dhns.DhnsPersistenceProvider.readXML(DhnsPersistenceProvider.java:49)
 at org.gephi.project.io.GephiReader.readWorkspaceChildren(GephiReader.java:145)
 at org.gephi.project.io.GephiReader.readWorkspace(GephiReader.java:131)
 at org.gephi.project.io.GephiReader.readProject(GephiReader.java:104)
 at org.gephi.project.io.GephiReader.readAll(GephiReader.java:81)
 at org.gephi.project.io.LoadTask.run(LoadTask.java:76)
 at org.gephi.utils.longtask.api.LongTaskExecutor$RunningLongTask.run(LongTaskExecutor.java:227)
 at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
 at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
 at java.util.concurrent.FutureTask.run(FutureTask.java:138)
 at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
 at java.lang.Thread.run(Thread.java:619)