UI: Fix twitch stream stat window not centering

Fixes an issue where if you auth to twitch, then close the program
without unhiding the twitch stream stats panel, the next time that panel
was unhidden it would be at position 0,0 on your screen.  This
explicitly sets its position to be center of the window beforehand to
ensure that won't occur.

UI/auth-twitch.cpp

@@ -248,6 +248,7 @@ void TwitchAuth::LoadSecondaryUIPanes()
 	std::string url;
 	std::string script;
 
+	QSize size = main->frameSize();
 	QPoint pos = main->pos();
 
 	script = "localStorage.setItem('twilight.theme', 1);";
@@ -304,7 +305,11 @@ void TwitchAuth::LoadSecondaryUIPanes()
 	info->setFloating(true);
 	stat->setFloating(true);
 
+	QSize statSize = stat->frameSize();
+
 	info->move(pos.x() + 50, pos.y() + 50);
+	stat->move(pos.x() + size.width()  / 2 - statSize.width()  / 2,
+	           pos.y() + size.height() / 2 - statSize.height() / 2);
 
 	if (firstLoad) {
 		info->setVisible(true);