Attribute dialog does not open when attribute is read-only

[Geert Bellekens]

When a package is readonly because of a security, or version control lock, EA refuses to open the new attribute properties dialog.
When right clicking on the attribute in the project browser and selecting Properties | Properties EA shows an error message saying:
"The current action cannot be completed as the necessary security is not available"

Pressing F9, or opening the properties from the features windows does not show this error message.

Tested on v15.0.1512

Reported

Geert