fix(ui): restore splitter state

Fixes qTox#4387 and qTox#2378.

This restores the state of the splitter correctly from settings in
multiple window mode and if this mode is quited.

src/widget/contentdialog.cpp

@@ -124,7 +124,7 @@ ContentDialog::ContentDialog(SettingsWidget* settingsWidget, QWidget* parent)
     }
 
     SplitterRestorer restorer(splitter);
-    restorer.restore(s.getDialogSettingsGeometry(), size());
+    restorer.restore(s.getDialogSplitterState(), size());
 
     currentDialog = this;
     setAcceptDrops(true);

src/widget/widget.cpp

@@ -662,6 +662,9 @@ void Widget::onSeparateWindowChanged(bool separate, bool clicked)
 
         setMinimumWidth(775);
 
+        SplitterRestorer restorer(ui->mainSplitter);
+        restorer.restore(Settings::getInstance().getSplitterState(), size());
+
         onAddClicked();
     } else {
         int width = ui->friendList->size().width();