ID 416984 - The behaviour of the sendToViewer() function has changed in Hiero 12

Problem summary
The behaviour of the sendToViewer() function has changed in Hiero 12. 
When changing track visibility via Python, the Viewer remains black until the track is manually disabled and re-enabled.

Customer reported version
Hiero 12

Customer reported platform
CentOS 7

Steps to reproduce

1) Open Hiero

2) Import some clips and add them to separate tracks on the Timeline 

3) Run the following code in the Script Editor 

seq = hiero.ui.activeSequence()
te = hiero.ui.getTimelineEditor(seq)
view = hiero.ui.activeView()
viewer = hiero.ui.currentViewer()
player = viewer.player()

bi = seq.binItem()
vts = seq.videoTracks()


for vt in vts:
    name = vt.name()

    if name == "Video 1":
        vt.setEnabled(1)
    else:
        vt.setEnabled(0)

hiero.ui.sendToViewerA(bi)
player.centerImage()

Expected behaviour
The enabled track should appear in the Viewer.

Actual behaviour
The Viewer remains black until the track is manually disabled and re-enabled.

Reproduced by support
This bug has been reproduced in:
Hiero 12.0v3 - Windows 10 - macOS 10.14 (Mojave) - CentOS 7
Hiero 12.0v1 - Windows 10 - macOS 10.14 (Mojave) - CentOS 7 - Regression

Unable to reproduce bug in:
Hiero 11.3v6 - Windows 10 - macOS 10.14 (Mojave) - CentOS 7

Earliest version tested
Hiero 11.3v6
- This issue doesn't appear in this version and has regressed