please merge 19846
This fixes the case when the user launch some actions while the buffer is loading, jEdit may have some exceptions.
A bug reported that
This is easy to reproduce :
try to load a big buffer on a slow filesystem http://www.ietf.org/rfc/rfc3261.txt for example and press ctrl+A to select all quickly or End to go to end of line.
This can also be merged in 4.3