viewerpanelbase: stop playback when panel is defocused

app/panel/panelmanager.cpp

@@ -28,7 +28,8 @@ PanelManager* PanelManager::instance_ = nullptr;
 
 PanelManager::PanelManager(QObject *parent) :
   QObject(parent),
-  locked_(false)
+  locked_(false),
+  suppress_changed_signal_(false)
 {
 }
 
@@ -165,7 +166,9 @@ void PanelManager::FocusChanged(QWidget *old, QWidget *now)
           focus_history_.move(panel_index, 0);
         }
 
-        emit FocusedPanelChanged(panel_cast_test);
+        if (!suppress_changed_signal_) {
+          emit FocusedPanelChanged(panel_cast_test);
+        }
       }
 
       break;