visualizer makefile: don't error on clean if jar doesn't exist
visualizer makefile: don't error on clean if jar doesn't exist

[ci skip]

jbush001/NyuziProcessor,jbush001/NyuziProcessor,jbush001/NyuziProcessor,jbush001/NyuziProcessor,FulcronZ/NyuziProcessor,FulcronZ/NyuziProcessor,FulcronZ/NyuziProcessor,FulcronZ/NyuziProcessor,jbush001/NyuziProcessor,jbush001/NyuziProcessor