Problem plotting operations with 0 execution time starting at schedule_time

Run secondorderdirectformiir.py and extract the operations. out1 starts at time 7 and has execution time 0, but is drawn like this:

Not obvious if it should be allowed, but it would be nice visually if operations with zero execution time can start at schedule_time...

(Maybe this is the same issue as with the incorrect left-edge algorithm? That it is actually a zero time memory variable, but it looks like it covers the whole schedule time?)