https://forum.plantuml.net/9816/pipemap-returns-non-zero-exit-code-even-on-success was fixed in 2019.8.
However, another bug was introduced. With older versions, you could run -pipemap without any links in the diagram, and it would return a 0 exit code:
$ echo "a -> b" | java -jar plantuml.jar -pipemap
Picked up JAVA_TOOL_OPTIONS: -Xmx500m
$ echo $?
0
But in 2019.8 it returns an error and a non-zero exit code:
$ echo "a -> b" | java -jar plantuml.jar -pipemap
Picked up JAVA_TOOL_OPTIONS: -Xmx500m
No diagram found
$ echo $?
100