Fix regression with initial sorting after pr205

[hebasto]

Unfortunately, #205 introduced a regression. After opening the "Receive" or "Transaction" tab at first time despite of the "Date" header is marked as sorted, table rows are not sorted actually:

It appears that sorting the table must be triggered after the QTableView::setModel call.

With this PR (and pre-#205):

[hebasto]

Many thanks to @Geremia who reports about this regression.

[leonardojobim]

Tested ACK c524dc5 on Ubuntu 20.04.2 Qt 5.12.8

I can confirm the "Transactions" table rows are not initially ordered on the master branch. And this PR fixes this.

However, in my node, the "Receive" table rows are correctly ordered, both on the master and on this PR branch.

Transactions table on master branch	Transactions table on this PR branch	Both ("Receive" table)

[Talkless]

tACK c524dc5, tested on Debian Sid with Qt 5.15.2. I can confirm @leonardojobim observations.

[jonatack]

ACK c524dc5

[jarolrod]

ACK c524dc5, tested on macOS 11.1 Qt 5.15.2

Confirming this regression on master and that this PR fixes it. I see the same behavior as shown in @leonardojobim screenshots.

This regression can actually be seen in my review of the PR that introduced the bug: #205 (review). It's not immediately obvious that the PR introduced this bug because all of the transactions occurred under the same minute. The maturity indicator is the clue that shows that the transactions we're not sorted by date under this PR.

This highlights the need for increased test coverage of the GUI.

[laanwj]

Thanks for fixing this, can confirm that it works.