Fix crash with InCA without accelerator
This crash can be achieved with the following user code:
from pyjapc import PyJapc
japc1 = PyJapc(incaAcceleratorName='')
japc2 = PyJapc(incaAcceleratorName='')
Test is not trivial to add, as parts of the IncaConfigurator
would need to be mocked (InCA server communication hangs in non-TN locations).