Tree DnD: drop twice the same object results in obscure error message.

[guest]

With Firefox, an exception occurs when you're trying to drop twice the same object in the same tree.

Exception: [Exception... "'Error: assertion failed in ItemFileWriteStore?' when calling method: [nsIDOMEventListener::handleEvent]" nsresult: "0x8057001c (NS_ERROR_XPC_JS_THREW_JS_OBJECT)" location: "<unknown>" data: no]

[bill]

That's correct, an exception occurs since you can't add the same item to a store twice. Not sure how to fix this or even what the UI should be to inform the user of their error, but will look into it. Perhaps the drag icon would be red to begin with (maybe checkAcceptance() should check if the item already exists), although that doesn't really tell the user what the problem is.

[bill]

For now the application has to work around this... as I said above you can problem catch it w/a custom version of checkAcceptance().