No Checking (Permission/Notification Schemes) When Removing a Custom Field

When removing a custom field (e.g multi user picker, user picker), there is no checking to check if the custom field is being used in the notification schemes or permission schemes.

2008-01-21 11:36:30,329 http-55445-Processor22 ERROR [webwork.util.ServletValueStack] METHOD: "argumentDisplay", exception: 
java.lang.IllegalArgumentException: Custom field with id 'customfield_10031' does not exist.
	at com.atlassian.jira.issue.fields.DefaultFieldManager.getCustomField(DefaultFieldManager.java:618)
	at com.atlassian.jira.notification.type.UserCFValue.getArgumentDisplay(UserCFValue.java:144)
...

This is the error that will be thrown by JIRA when an invalid custom field is viewed at the notification schemes. The more this custom field is used in the notification schemes, the more the error will be thrown and the longer it takes to load the notification scheme.