Remove redundant infill_pattern checks.
Remove redundant infill_pattern checks.

As infill_angles will only contain elements when the infill method is lines
or zig zag, checking that its size is > 0 is sufficient, we don't also need
to check the infill_pattern.

ROBO3D/CuraEngine,alephobjects/CuraEngine,Ultimaker/CuraEngine,Ultimaker/CuraEngine,ROBO3D/CuraEngine,alephobjects/CuraEngine,ROBO3D/CuraEngine,alephobjects/CuraEngine