Temporary quick-look file not removed after gpt execution

Dear developers,

I noticed that when running gpt, a temporary quick-look.png file is created. However, after the execution, the file remains there.
I used the graph file below as an example with a simple Read operation.

This is the command:

/opt/s1tbx-snap4.0/bin/gpt -Djava.io.tmpdir=/home/user/tmp -e S1A_IW_SLC__1SDV_20161016T163023_20161016T163050_013517_0159FA_A46B_GRAPH.xml

This is the graph file:

<graph id="Graph">
  <node id="1-Read">
    <sources />
    <parameters class="com.bc.ceres.binding.dom.XppDomElement">

Before executing the command, the temporary directory is empty.
Afterwards, it contains a tree of directories with a preview image in the deepest directory:

I expected the temporary folders and preview file to be removed after the execution of the command, but it doesn’t happen.
Is this a bug?

Thank you.