Unable to Export?

RapidWeaver Version: Version 6.3 (14965)
System Version: 10.10.4
Hardware: iMacBook 27’, 3,5 GHz Intel Core i7 Processor, 1,12 To Fusion Drive Storage, 32 Go 1600 MHz DDR3.

Hi there,
When i’ve updated RW this morning, i was worked on our new web project (which is online thanks to the publishing function ;)).
After RW restarted (OS X too), it was impossible to correctly re-open the project… When i “clic clic” on the Project file, it opens but nothing appears. All stacks are invisible and in the left merge, i can see the plan of the site (Pages tab) with blue dots…
When i made some action as going to preview : i can see a popup :

Exception while exporting site
-[__NSCFString appendString:]: nil argument

When i clic OK to close the popup, the page tries to be exported (normal) but another notification is shown in the right top corner of the screen : Unable to Export. I close the popup and that’s all… can’t work…

Any idea? :sob: