Fix error when editing Pattern Blocks

[maugelves]

When a user tries to edit a Block Pattern in the content itself, the plugin throws this error:

TypeError: Cannot read properties of undefined (reading 'length')
    at AuthorsSelect (AuthorsSelect.tsx:61:1)
    at wt (react-dom.min.js?ver=18.2.0:10:47637)
    at js (react-dom.min.js?ver=18.2.0:10:120584)
    at wl (react-dom.min.js?ver=18.2.0:10:88659)
    at bl (react-dom.min.js?ver=18.2.0:10:88587)
    at yl (react-dom.min.js?ver=18.2.0:10:88450)
    at il (react-dom.min.js?ver=18.2.0:10:85274)
    at fl (react-dom.min.js?ver=18.2.0:10:85661)
    at Nn (react-dom.min.js?ver=18.2.0:10:32474)
    at react-dom.min.js?ver=18.2.0:10:83226

Adding an extra check in a conditional fixed the problem.

[roborourke]

Thanks @maugelves, I guess this is an issue when the editor now switches contexts between post types that support authorship and those that don't, or don't have set yet.

Makes me think this change in core will impact a lot of existing features / functionality :/