Fix TimelineController height calculation.

server/TracyView_Timeline.cpp

@@ -333,6 +333,7 @@ void View::DrawTimeline()
 
     const auto wpos = ImGui::GetCursorScreenPos();
     const auto dpos = wpos + ImVec2( 0.5f, 0.5f );
+    // note that m_tc.GetHeight() returns the height from the previous draw
     const auto h = std::max<float>( m_tc.GetHeight(), ImGui::GetContentRegionAvail().y - 4 );    // magic border value
 
     ImGui::ItemSize( ImVec2( w, h ) );