bug fix in L1Vector

The MR fixes a bug in L1Vector reported here: https://lxcbmredmine01.gsi.de/issues/2093

reco/L1/CbmL1Def.h

@@ -121,11 +121,11 @@ public:
     return std::vector<T>::operator[](index);
   }
 
-  const char* getName()
+  std::string getName()
   {
     std::string s = " L1Vector<";
     s += fName + "> ";
-    return s.data();
+    return s;
   }
 
 private: