-svg.svg file is not getting created after creating the process in JBPM7.1.0

Hi
I am new to JBPM and installed JBPM 7.1.0 final version in my machine. I was trying to create a simple process in sample example. I was able to run the sample project initially with start node, script task and end node. After some time I was trying to create sample example and trying to save then it was reporting Failed to save null Asset. When I observed number of files got created after created the process.
1. Working scenario
once I created the simple process then editor getting created simpleproject.exprocess-svg.svg , exprocess.bpmn2 file and WorkDefination.wid file
able to save and run the instance

2. Not working scenario
sometimes when I try to create the simple process then it was creating only two files
exprocess.bpmn2 file and WorkDefination.wid file

Due to this when I saveing it was reporting the Failed to save null Asset.

Able to see example is working when all 3 files got created and not working when -svg.svg file was not getting created.

I tried removing the folder .niogit and retried and getting same exception.

can you help in fixing this issue
Thanks
Subbu