WMF plugin: Initialize member variable m_stateDirty.

Fix purify warning:
[W] UMR: Uninitialized memory read in MFPlayerControl::refreshState(void) {1 occurrence}

Task-number: QTBUG-41966
Change-Id: I1416f906dcc8c31a528ab7f09a258873fcfe9d1e
Reviewed-by: Yoann Lopes <yoann.lopes@theqtcompany.com>

src/plugins/wmf/player/mfplayercontrol.cpp

@@ -39,6 +39,7 @@
 MFPlayerControl::MFPlayerControl(MFPlayerSession *session)
 : QMediaPlayerControl(session)
 , m_state(QMediaPlayer::StoppedState)
+, m_stateDirty(false)
 , m_videoAvailable(false)
 , m_audioAvailable(false)
 , m_duration(-1)