error adding file to Whiteboard

[Aaron Hepp]

While I know why it causes the error, is there a way to throw a message 
instead of sending the user to the "Internal Error" page.

If no Whiteboard is open and a user uploads a file and "send directly to 
whiteboard" it boots the user and sends them to the "internal Error" 
page.  While this is understandable why it does that; Is there a way 
instead of redirecting to that page just prompt a warning message about 
no whiteboard selected?

Didn't know if this would require too much code change or a quick fix.  
If a lot, then I would not worry about it, just something I noticed when 
a user tried.

Thanks.