fix: currentMediaInfo undefined causing buffer change

[adrums86]

Description

currentMediaInfo_ is becoming undefined due to a change in playlists from ABR, this is eventually causing a call to addOrChangeSourceBuffers via a trackinfo event which will throw an error trying to change the source buffer unnecessarily.

Specific Changes proposed

check if currentMediaInfo_ is defined before comparing to the trackInfo.

Requirements Checklist

• [x] Feature implemented / Bug fixed
• [ ] If necessary, more likely in a feature request than a bug fix
  • [ ] Unit Tests updated or fixed
  • [ ] Docs/guides updated
  • [ ] Example created (starter template on JSBin)
• [ ] Reviewed by Two Core Contributors

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (c726760) 86.01% compared to head (46bb7e6) 85.91%. Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1462 +/- ## ========================================== - Coverage 86.01% 85.91% -0.10% ========================================== Files 42 42 Lines 10673 10672 -1 Branches 2456 2456 ========================================== - Hits 9180 9169 -11 - Misses 1493 1503 +10 ```

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[adrums86]

Closing this as it didn't turn out to be the correct solution.