Asset libraries from the Preferences were not recognized as such. This
could cause various issues like the asset library not being refreshed
correctly on relevant changes. There was also a failed assert when
right-clicking the context menu of a custom brush asset, and the "Edit
Metadata" brush asset operator would be unavailable.
A pointer was unintentionally cast to a boolean, and instead null passed
for the pointer (because of a default argument value).
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