🐛 | Field CSS | Notice: Undefined index: field_MY_css in Drupal\field_css\Traits\CssTrait::itemPrefixes() (line 36 of modules/contrib/field_css/src/Traits/CssTrait.php).
🇨🇳China carlxjs
The patch file in #2 can not apply in 2.0.x-dev now.
So I make a new patch for 2.0.x-dev.