VideoManager: Remove pointer check before delete

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

src/FlightDisplay/VideoManager.cc

@@ -39,12 +39,10 @@ VideoManager::VideoManager(QGCApplication* app, QGCToolbox* toolbox)
 //-----------------------------------------------------------------------------
 VideoManager::~VideoManager()
 {
-    if(_videoReceiver) {
     delete _videoReceiver;
-    }
+    _videoReceiver = nullptr;
-    if(_thermalVideoReceiver) {
     delete _thermalVideoReceiver;
-    }
+    _thermalVideoReceiver = nullptr;
 }
 
 //-----------------------------------------------------------------------------