Custom field doesn't show in bulk edit if it has multiple contexts

Issue Summary

If a custom field has multiple contexts and issues from different projects in more than one context are selected in bulk edit, the custom field won't show up even if doesn't have a different set of options in each context (text field, labels, etc...)

Steps to Reproduce

1. Create a custom field with type labels.
2. Create two contexts with a different set of projects.
3. Run a bulk edit on issues from two projects that are present in different contexts.
4. Make sure the custom field is present in the edit screens of the two projects and issue types being edited.

Expected Results

The custom field should be present in the bulk edit screen.

Actual Results

Custom field is not present. However, if the issues selected to be edited are from projects within the same custom field context, the field will shop up.

Workaround

Edit the issues from projects within the same context together.