This bug is still existing with iOS 26.

This problem only occurs on Xcode 15. It works on Xcode 14 as the CompileAssetCatalog command isn't executed. This is due to a new feature from Xcode 15 regarding Asset Catalogs (https://developer.apple.com/documentation/xcode-release-notes/xcode-15-release-notes#Asset-Catalogs). Still, I couldn't find any reason why it doesn't work, with such a wrong error message. But at least I could work my way around by disabling this new feature by setting ASSETCATALOG_COMPILER_GENERATE_ASSET_SYMBOLS to NO in my project's build settings.