fix bug if group number is 0 (possible when a contaminant protein is removed)

src/core/proteinmatch.cpp

@@ -790,11 +790,11 @@ ProteinMatch::setGroupInstance(GroupStore &group_store)
     {
       unsigned int group_number = _sp_grp_protein.get()->getGroupNumber();
       qDebug() << "group_number=" << group_number;
-      // if(group_number > 0)
-      // {
-      _sp_group = group_store.getInstance(group_number);
-      _sp_group.get()->add(this);
-      // }
+      if(group_number > 0)
+        {
+          _sp_group = group_store.getInstance(group_number);
+          _sp_group.get()->add(this);
+        }
     }
   qDebug();
 }