split: clamp minimum split size to 1

The split command allows delta size changes, which triggers a condition
where the split can overflow into the dirlist. Clamp the minimum size of
a split or vsplit to "1" to prevent the view from overflowing, or
completely covering the message list. A split of 0 will still clear the
split.

Reported-by: Koni Marti <koni.marti@gmail.com>
Signed-off-by: Tim Culverhouse <tim@timculverhouse.com>
Acked-by: Robin Jarry <robin@jarry.cc>

commands/account/split.go

@@ -57,6 +57,10 @@ func (Split) Execute(aerc *widgets.Aerc, args []string) error {
 		// toggling the split
 		n = 0
 	}
+	if n < 0 {
+		// Don't allow split to go negative
+		n = 1
+	}
 	if args[0] == "split" {
 		return acct.Split(n)
 	}