issue #8474: Crash: double free or corruption (out)

Author: doxygen

src/ftvhelp.cpp

@@ -701,7 +701,7 @@ static void generateJSNavTree(const std::vector<FTVNode*> &nodeList)
 
     // write the navigation index (and sub-indices)
     std::sort(navIndex.begin(),navIndex.end(),[](const auto &n1,const auto &n2)
-        { return qstrcmp(n1.url,n2.url)<0; });
+        { return !n1.url.isEmpty() && (n2.url.isEmpty() || qstrcmp(n1.url,n2.url)<0); });
 
     int subIndex=0;
     int elemCount=0;