Performing seamless server travel while a Legacy Camera Shake with an Anim Sequence set is ongoing will cause a crash

When we server travel with seamless travel enabled, and a legacy camera shake with an anim sequence set is currently ongoing, we will get a crash due to the UMovieSceneEntitySystemLinker failing a check. This only occurs when seamless traveling and only with legacy camera shakes that have an anim sequence set. This occurs both in PIE and packaged builds.

• Create two new levels, a start level and a destination level
• Create a new game mode with Use Seamless Travel set to true
• Use this game mode in the two new levels
• Create a new camera animation sequence
• Create a new blueprint class derived from LegacyCameraShake
• Set the Anim Sequence in the new legacy camera shake class to the new camera animation sequence
• Optionally set some oscillation values to make it easier to debug that the camera shake is playing
• On the begin play of the start level include the following:
• Execute the console command: net.AllowPIESeamlessTravel true
• Start the camera shake of the new legacy camera shake class
• Delay for some amount of time less than the duration of the camera shake
• Start Server Travel to the destination level
• Observe a crash upon commencing server travel