ID 437214 - Crash when querying data from null trackItems

Problem summary
Crash when querying data from null trackItems

From testing, this includes at least:

trackItem.duration()
trackItem.timelineIn()
trackItem.timelineOut()

Customer reported version
hiero.12.1v2

Customer reported platform

OSX

Steps to reproduce

1) Open NukeStudio/Hiero

2) Create a new Sequence, and load it into the Timeline view

3) Open the Script Editor and run the following code:

seq = hiero.ui.activeSequence()
ti = seq.trackItemAt(0)
ti.timelineOut()

* changing .timelineOut() for .timelineIn() or .duration() also reproduces the issue

Expected behaviour

For it to error saying:

RuntimeError: TrackItem is null

as it does for ti.currentVersion()

Actual behaviour
NukeStudio/Hiero crash

Workaround
Don't run the code on null items, which you can check for by using ti.isNull()

Reproduced by support
This bug has been reproduced in:

NukeStudio 12.1v2  - Windows 10, CentOS 7

NukeStudio 12.0v1  - Windows 10

NukeStudio 11.0v1  - Windows 10

NukeStudio 10.0v1  - Windows 10, CentOS 7

Unable to reproduce bug in:
NukeStudio 9.0v9  - Windows 10 * trackItemAt() returns None, rather than a null trackItem

Earliest version tested
NukeStudio 10.0v1 - This feature did not exist before this version