Find the worker clone of a module by name

OwnModule looked the clone up by the position of the master's module, which relied on both lists having the same order.

https://its.cern.ch/jira/browse/O2-7305

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: sawenzel

Detectors/3rdparty/FairRootBase/src/FairMCApplication.cxx

@@ -616,19 +616,15 @@ TVirtualMCApplication* FairMCApplication::CloneForWorker() const
 //_____________________________________________________________________________
 FairModule* FairMCApplication::OwnModule(FairModule* module) const
 {
-    // On a worker, the sensitive volumes still refer to the master's modules; the clones are in the same order
-    if (!module || IsMasterApplication()) {
+    // the worker's clone of a module, found by name
+    if (!module || IsMasterApplication() || fModules->IndexOf(module) >= 0) {
         return module;
     }
-    // volumes registered by the worker's own clones (in their Initialize) already point at them
-    if (fModules->IndexOf(module) >= 0) {
-        return module;
-    }
-    Int_t index = fgMasterInstance->fModules->IndexOf(module);
-    if (index < 0 || !fModules->At(index)) {
+    auto clone = static_cast<FairModule*>(fModules->FindObject(module->GetName()));
+    if (!clone) {
         LOG(fatal) << "FairMCApplication: no worker clone for module " << module->GetName();
     }
-    return static_cast<FairModule*>(fModules->At(index));
+    return clone;
 }
 
 //_____________________________________________________________________________