Navigating to a branch which is currently locked should produce a more helpful result

[Martitza]

Steps to reproduce:

0. start at the "welcome" page
1. "open" an existing branch
2. start a time-consuming operation like a pull
3. switch back to the welcome page
4. "open" another existing branch
5. switch back to the welcome page
6. switch back to the first branch, while the pull is still in progress ==> DIALOG!

Observed:
The dialog has a scary-to-a-newbie message about not being able to get a lock.
The options are to close the app or ignore the problem. Close shuts down the app, and Ignore leaves the welcome page open.

Expected:
I propose that a better solution would be for the dialog to offer something like "The view you have requested is busy. Press Wait to wait for it to be ready or Ignore to go back to what you were doing." Notice that Close would not be an option. Close is really not helpful. I just end up having to restart Explorer anyway.

[Alexander Belchenko (bialix)]

I think the best here for explorer is just silently ignore lock error and swicth to the branch. I suspect the explorer want to update the branch information when you switch to it but failed to do so. But this is not fatal error, so we should not scary the users.