Fix crash when element is being inserted "after itself"

tinyxml2.cpp

@@ -911,6 +911,13 @@ XMLNode* XMLNode::InsertAfterChild( XMLNode* afterThis, XMLNode* addThis )
         TIXMLASSERT( false );
         return 0;
     }
+    if ( afterThis == addThis ) {
+        // Current state: BeforeThis -> AddThis -> OneAfterAddThis
+        // Now AddThis must disappear from it's location and then
+        // reappear between BeforeThis and OneAfterAddThis.
+        // So just leave it where it is.
+        return addThis;
+    }
 
     if ( afterThis->_next == 0 ) {
         // The last node or the only node.