PseudoConstant - Prevent fatal when entity not available

[colemanw]

Overview

Prevents a hard-crash in certain scenarios when metadata is being loaded for an entity that doesn't exist. This is especially likely to happen during upgrades, particuarly the upgrade to 5.64 due to #26208

Before

More crashy

After

Less crashy

Technical Details

This can happen e.g when Views tries to lookup an option value for a disabled extension. See civicrm/civicrm-drupal#656 (comment)

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[demeritcowboy]

Thanks. Putting merge-on-pass since it does seem safe.
I'll put up a small tweak for views for e_notice.

[demeritcowboy]

Hmm lots of test fails that seem real.

[colemanw]

Take 2