On magnolia-ui-m6, A NullPointerException is thrown at info.magnolia.ui.form.field.definition.FieldDefinitionKeyGenerator.keysFor(FieldDefinitionKeyGenerator.java:64)
when one opens a dialog containing a link field where the "field" node does not have a "label" property. The same dialog does open correctly when configured via bootstrap.
Example dialog file attached.
When a label is added to the field node - then it works correctly.