[RF] fix memleak in RooAbsCollection::find()

#18322

Author: ferdymercury

roofit/roofitcore/src/RooAbsCollection.cxx

@@ -929,6 +929,8 @@ RooAbsArg * RooAbsCollection::find(const char *name) const
 
   if (_hashAssistedFind || _list.size() >= _sizeThresholdForMapSearch) {
     if (!_hashAssistedFind || !_hashAssistedFind->isValid()) {
+      if (_hashAssistedFind)
+         delete _hashAssistedFind;
       _hashAssistedFind = new HashAssistedFind{_list.begin(), _list.end()};
     }