You can give yourself a missing texture banner with commands with no resource packs

The missing texture is only supposed to show if there exists a problem with the active resource pack, and the vanilla resource pack should be entirely bug-free. Despite this, there appear to be no checks on whether a banner item has a valid inline defined banner pattern component, resulting in the missing texture checker being encounterable in pure vanilla, without having to pass in a broken resource pack or data pack.

To reproduce, run this command: /give @s minecraft:white_banner[minecraft:banner_patterns=[{pattern:{asset_id:"minecraft:some_nonexistent_pattern_type",translation_key:""},color:"white"}]]

Expected results: the command would be rejected due to the invalid specified banner pattern, or the invalid banner pattern would be stripped out and replaced by a default fallback value.

Actual results: the game treats the banner as valid, has no texture to point to, and instead throws out a missing texture error.