DrawGratings dependency on UpdateFrame can cause 'missed' render frames

[RoboDoig]

repro workflow

Spotted that when switching observables that contain draw gratings, often there are blank frames in between initialisation. This can happen if e.g. a Timer aborts the observable and seems to interrupt the rendering of the grating.

In discussion with @glopesdev - noticed that this is specific to DrawGratings and that it is caused by DrawGratings dependence on UpdateFrame internally, that means WithLatestFrom is dependent on an update step.

[chiyu1203]

@RoboDoig thanks for pointing this out! So, is there any way to fix this issue? And I guess any workflow using animated stimuli that is controlled by UpdateFrame internally would bump into this issue?!