Pressing `Enter` on a view that has not yet loaded messages (e.g. at
startup) would return `nil` from `Selected()`. Accessing `msg.Uid` on a
`nil` reference crashes aerc.
This patch moves the `msg == nil` check before accessing `msg.Uid` thus
avoiding the crash.
To test this patch repeatedly press `Enter` on startup.
Allowing the user to view deleted messages creates all sorts of race
conditions. The most devious race condition is pv.source can be set to a
nil while another PartViewer is still running a goroutine in
attemptCopy.
Here is a trace when this happens.
goroutine 76 [running]: io.copyBuffer(0x7f8ad02641d0, 0xc00040f590, 0x0,
0x0, 0xc0007cc000, 0x8000, 0x8000, 0x0, 0x0, 0x8b3d60)
/usr/lib/go/src/io/io.go:402 +0x101 io.Copy(...)
/usr/lib/go/src/io/io.go:364
git.sr.ht/~sircmpwn/aerc/widgets.(*PartViewer).attemptCopy.func4(0xc00017efd0,
0xc0004da7c0) /home/keur/repos/aerc/widgets/msgviewer.go:576 +0x611
created by git.sr.ht/~sircmpwn/aerc/widgets.(*PartViewer).attemptCopy
/home/keur/repos/aerc/widgets/msgviewer.go:544 +0x144
We could add a guard in store.FetchBodyPart to only call the callback
when msg.Part.Reader != nil, but we still get a hanging pager. Therefore
it seems more reasonable to disable this completely.
Signed-off-by: Kevin Kuehler <keur@xcf.berkeley.edu>
Consists of 3 functions
* Store: Access to MessageStore type
* SelectedAccount: Access to Account widget that the target widget
belongs to
* SelectedMessage: Current message (selected in msglist or the one we
are viewing)
Signed-off-by: Kevin Kuehler <keur@ocf.berkeley.edu>
