Fix return value of wxGenericTreeCtrl::FindItem().

We incorrectly returned the item we started from instead of invalid item if
there was no match, fix this.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72637 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/treectlg.cpp

@@ -1599,8 +1599,12 @@ wxTreeItemId wxGenericTreeCtrl::FindItem(const wxTreeItemId& idParent,
         {
             itemid = GetNext(itemid);
         }
-        // If we haven't found the item, id.IsOk() will be false, as per
-        // documentation
+        // If we haven't found the item but wrapped back to the one we started
+        // from, id.IsOk() must be false
+        if ( itemid == idParent )
+        {
+            itemid = wxTreeItemId();
+        }
     }
 
     return itemid;