Solved another potential dead lock when stopping.

Performances when moving along in the clip should be a little improved
in synchrone mode.

src/Workflow/MainWorkflow.cpp

@@ -175,16 +175,17 @@ void        MainWorkflow::previousFrame()
 
 void        MainWorkflow::setPosition( float pos )
 {
+    if ( m_renderStarted == false )
+        return ;
     //Since any track can be reactivated, we reactivate all of them, and let them
     //unable themself if required.
     for ( unsigned int i = 0; i < m_trackCount; ++i)
         m_tracks[i].activate();
 
-    if ( m_renderStarted == false )
-        return ;
     qint64  frame = static_cast<qint64>( (float)m_length * pos );
     m_currentFrame = frame;
     emit frameChanged( frame );
+    cancelSynchronisation();
     //Do not emit a signal for the RenderWidget, since it's the one that triggered that call...
 }
 

src/renderer/WorkflowRenderer.cpp

@@ -86,6 +86,9 @@ void*   WorkflowRenderer::lock( void* datas )
 {
     WorkflowRenderer* self = reinterpret_cast<WorkflowRenderer*>( datas );
 
+    //If renderer is stopping, don't ask for another frame:
+    if ( self->m_isRendering == false )
+        return self->m_lastFrame;
     //If we're not playing, then where in a paused media player.
     if ( self->m_pausedMediaPlayer == true )
     {