Method isClonable throws Plugin not found exception when target_type is not defined in field settings

This is a very specific case which would need proper steps to reproduce. When creating a custom entity without a bundle, the condition for $field_definition instanceof FieldConfigInterface is usually not met at least not when you want to throw something together to reproduce the issue. When adding a bundle the target_type is usually set. As this code additionally checks that the target_type is set, before loading the entity storage I see no harm in this being added, but will leave the status to needs review if somebody maybe has a custom entity at hand and can reproduce the issue.

It seems there is already a fix for this issue in 🐛 EntityCloneCloneableField isClonable fails when target_type setting is missing Active which also has more comments and MR is approved, so closing this as a duplicate.