FEM: Fix invalid check for empty resutls
FEM: Fix invalid check for empty resutls

Even when readResult was not producing any resuts the check was passing
fine as len({'Nodes': {}, 'Tet10Elem': {}, 'Results': []}) is 3

Signed-off-by: Przemo Firszt <ebf2bb805329591a27e694024b5e4c3c5da00121@firszt.eu>

timthelion/FreeCAD,chrisjaquet/FreeCAD,wood-galaxy/FreeCAD,chrisjaquet/FreeCAD,maurerpe/FreeCAD,bblacey/FreeCAD-MacOS-CI,wood-galaxy/FreeCAD,usakhelo/FreeCAD,chrisjaquet/FreeCAD,chrisjaquet/FreeCAD,timthelion/FreeCAD,kkoksvik/FreeCAD,kkoksvik/FreeCAD,kkoksvik/FreeCAD,usakhelo/FreeCAD,wood-galaxy/FreeCAD,wood-galaxy/FreeCAD,usakhelo/FreeCAD,usakhelo/FreeCAD,chrisjaquet/FreeCAD,bblacey/FreeCAD-MacOS-CI,kkoksvik/FreeCAD,maurerpe/FreeCAD,maurerpe/FreeCAD,Fat-Zer/FreeCAD_sf_master,chrisjaquet/FreeCAD,Fat-Zer/FreeCAD_sf_master,bblacey/FreeCAD-MacOS-CI,bblacey/FreeCAD-MacOS-CI,mickele77/FreeCAD,wood-galaxy/FreeCAD,mickele77/FreeCAD,mickele77/FreeCAD,maurerpe/FreeCAD,usakhelo/FreeCAD,timthelion/FreeCAD,timthelion/FreeCAD,wood-galaxy/FreeCAD,Fat-Zer/FreeCAD_sf_master,mickele77/FreeCAD,usakhelo/FreeCAD,Fat-Zer/FreeCAD_sf_master,kkoksvik/FreeCAD,timthelion/FreeCAD,timthelion/FreeCAD,mickele77/FreeCAD,bblacey/FreeCAD-MacOS-CI,chrisjaquet/FreeCAD,bblacey/FreeCAD-MacOS-CI,bblacey/FreeCAD-MacOS-CI,usakhelo/FreeCAD,Fat-Zer/FreeCAD_sf_master,maurerpe/FreeCAD