Fix textbox glitch : you could still type in the box after it lost its focus

git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/trunk@13092 178a84e3-b1eb-0310-8ba1-8eac791a3b58

src/guiengine/widgets/text_box_widget.cpp

@@ -145,6 +145,9 @@ void TextBoxWidget::unfocused(const int playerID, Widget* new_focus)
     assert(playerID == 0); // No support for multiple players in text areas!
 
     setWithinATextBox(false);
+    
+    if (new_focus != NULL)
+        GUIEngine::getGUIEnv()->setFocus(new_focus->getIrrlichtElement());
 }
 
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