Fixes parallelflow execution with no functions
Fixes parallelflow execution with no functions

If the module sent had no function, the max() call would raise
ValueError.

Nikea/VisTrails,celiafish/VisTrails,VisTrails/VisTrails,VisTrails/VisTrails,minesense/VisTrails,Nikea/VisTrails,VisTrails/VisTrails,celiafish/VisTrails,celiafish/VisTrails,minesense/VisTrails,Nikea/VisTrails,celiafish/VisTrails,Nikea/VisTrails,VisTrails/VisTrails,hjanime/VisTrails,minesense/VisTrails,minesense/VisTrails,hjanime/VisTrails,VisTrails/VisTrails,minesense/VisTrails,hjanime/VisTrails,hjanime/VisTrails,hjanime/VisTrails