Block type unexpectedly not registered when icon is '' or null in WordPress 5.3

[danielbachhuber]

Before WordPress 5.3, it was possible to register a block type using an empty string or null value for icon. This would result in the block type using the default 'block' icon.

In WordPress 5.3, a block type registered with icon: '' or icon: null will trigger this warning:

The early return statement added in 1a7255f#diff-bcd12caf7289c956a519c4cd8f3f363eR144-R150 causes the block type to not be registered.

My expectation is that a block type with icon: '' or icon: null would be registered with a default icon.

I took a look at the history of normalizeIconObject (https://github.com/WordPress/gutenberg/blame/a71241ca616642f6f590d6982fd82b46d96158ac/packages/blocks/src/api/utils.js#L85-L106). It seems like the last changes are a year old, so I'm not sure why we're only now experiencing this issue?

[tellthemachines]

I can confirm that this error is occurring when a block is registered with icon: '' or icon: null.

[gziolo]

Opened #34350 to address it.