Own regression caused by [0] made to ensure the string was initialized,
without accounting for it being static & reused between calls.
Replace static variables with a struct that's passed to the function,
this explicitly shares state between calls as this static variable use
depended on BKE_scene_multiview_view_prefix_get always clearing prefix
variables with a zero view_id so future calls would also be cleared.
While this non-obvious behavior could be documented,
use more straightforward logic.
[0]: bdad2c0595
0a125fccf4