Avoid dereference after null check

apps/openmw/mwgui/container.cpp

@@ -82,7 +82,7 @@ namespace MWGui
             dialog->eventOkClicked.clear();
             dialog->eventOkClicked += MyGUI::newDelegate(this, &ContainerWindow::dragItem);
         }
-        else
+        else if (mModel)
             dragItem (NULL, count);
     }
 

apps/openmw/mwgui/windowmanagerimp.cpp

@@ -898,7 +898,8 @@ namespace MWGui
 
         mKeyboardNavigation->onFrame();
 
-        mMessageBoxManager->onFrame(frameDuration);
+        if (mMessageBoxManager)
+            mMessageBoxManager->onFrame(frameDuration);
 
         mToolTips->onFrame(frameDuration);
 

apps/openmw/mwworld/worldimp.cpp

@@ -1180,9 +1180,9 @@ namespace MWWorld
                 addContainerScripts (getPlayerPtr(), newCell);
                 newPtr = getPlayerPtr();
             }
-            else
+            else if (currCell)
             {
-                bool currCellActive = currCell && mWorldScene->isCellActive(*currCell);
+                bool currCellActive = mWorldScene->isCellActive(*currCell);
                 bool newCellActive = newCell && mWorldScene->isCellActive(*newCell);
                 if (!currCellActive && newCellActive)
                 {