Why do I get the error “Save Failed index=0, size=0” in IBM Integration Designer when saving BPEL process with CatchAll block?

In IBM Integration Designer when working with BPEL Processes and creating a
CatchAll block into the fault handler, on an invoke activity or a scope,
I get a “Save Failed” error every time that the changes of that BPEL Process are saved.

What could be causing this?