Error when getting attributions of a BingMaps layer

Describe the bug
I sometimes have an error when getting the attributions of a BingMaps layer:

TypeError: Cannot read properties of undefined (reading '1')
    at BingMaps.js:315:43
    at Array.map (<anonymous>)
    at BingMaps.js:308:35
    at TileLayer.getAttributions (Layer.js:352:24)

When debugging, the coverrageArea object doesn't have a bbox property:

{"zoomMin":1,"zoomMax":21,"jsonBoundingBox":[-90,-180,90,180],"boundingBox":{"northeast":{"type":"Point","coordinates":[90,180]},"southwest":{"type":"Point","coordinates":[-90,-180]},"southLatitude":-90,"westLongitude":-180,"northLatitude":90,"eastLongitude":180}}

To Reproduce
I don't know when this happens. It works correctly most of the time...

Steps to reproduce the behavior:

1. Add a BingMaps layer
2. In a 'postrender' event, call getAttributions on the BingMaps layer

Expected behavior
No error in the console

Start in BingMaps.js around lines 308-315, then inspect Layer.js around getAttributions. Reproduce with a BingMaps layer and a postrender handler calling getAttributions, especially when coverageArea has boundingBox but no bbox. Done means attribution lookup completes without a console error.