im: fix wrong disconnect

- connection object captured could'nt be good
- also fix wrong usage of messagePresent variable

Change-Id: Ie75dc0d3a5d31108b4830972d372ac2bdbc19e36
Tuleap: #232

callwidget.cpp

@@ -613,10 +613,14 @@ CallWidget::on_contactMethodComboBox_currentIndexChanged(const QString& number)
         ui->listMessageView->setVisible(messagesPresent);
         ui->noMessagesLabel->setVisible(!messagesPresent);
         if (not messagesPresent) {
-            QMetaObject::Connection connection = connect(txtRecording->instantMessagingModel(), &QAbstractItemModel::rowsInserted, [&]() {
+            imVisibleConnection_ = connect(txtRecording->instantMessagingModel(),
+                                           &QAbstractItemModel::rowsInserted,
+                                           [this, txtRecording]() {
+                if (imVisibleConnection_)
+                    disconnect(imVisibleConnection_);
+                auto messagesPresent = txtRecording->instantMessagingModel()->rowCount() > 0;
                 ui->listMessageView->setVisible(messagesPresent);
                 ui->noMessagesLabel->setVisible(!messagesPresent);
-                disconnect(connection);
             });
         }
     }

callwidget.h

@@ -103,6 +103,7 @@ private:
     QModelIndex highLightedIndex_;
     ImDelegate* imDelegate_;
     QMetaObject::Connection imConnection_;
+    QMetaObject::Connection imVisibleConnection_;
     QPropertyAnimation* messagingPageAnim_;
     QPropertyAnimation* welcomePageAnim_;