Flattening tracks sometimes splits contiguous clips into segments

[jminor]

Incorrect Functionality

If a track has adjacent Gaps, then items below the boundary between those Gaps are sliced in an unexpected way.

To Reproduce

Using this test file "bug_before_flatten_redacted.otio"...
flatten_bug_repro.zip

Run this command:

% otiotool -i bug_before_flatten_redacted.otio --flatten video -o out.otio

Expected Behavior

Clips below adjacent Gaps should not be segmented by the flatten operation. In the provided example, Clip #1 should be left as-is.

Screenshots

Here is a screenshot before flattening (note the highlighted Gap on the top track)

Here is the result after flattening (note that Clip #1 has been split in two)

[douglascomet]

Seems related to the behavior outlines in #1430