Twitter profile widget form loses its values when re-edited

Issue Summary

Steps to reproduce :
Create a new widget set, then add element "Twitter profile widget" and fill some fields like width or colors, and "Update set"
=> the preview is correct
Then click on modify for the element just added : the form is empty (values are not prefilled).

The values are saved, however, because the widget reflects the settings.

With the widget "Facebook like box" the form is well prefilled.

I'm using socialmedia (7.x-1.0-beta8) and widgets (7.x-1.0-beta3). The widgets are provided by socialmedia, I don't know which module is concerned by this problem, so I post an issue in the two sides...