"Un-select all" is not functional in Messaging app

[Evan Wang]

$ system-image-cli -i
current build number: 46
device name: arale
channel: ubuntu-touch/tangxi/devel-proposed
last update: 2015-05-19 06:44:43
version version: 46
version device: 1e1b1cebe8900f5b62bed050a5c23a7765e62600d394cba528169d257e6ab36c
version custom: 8274419d06b4da1424e7f7339ff2f8276b38951951d8900e148a4fdfce8fba0d

Steps to reproduce:
1.Launch Messaging app
2.Hold down on one already existed message
3.Tap on "Select all" button on top right corner, all messages are selected
4.Tap on "Select all" button again

Expected results:
All messages are not selected

Actual results:
All messages are still selected

[Sebastien Bacher (seb128)]

Confirmed, the MainPage

                    onTriggered: threadList.selectAll()

should probably be changed to be similar to the version from the dialer

" onTriggered: {
                        if (historyList.selectedItems.count === historyList.count) {
                            historyList.clearSelection()
                        } else {
                            historyList.selectAll()
                        }
                    }"