alternative fix for the same problem that 9e2048decf was addressing

libs/ardour/session_state.cc

@@ -2888,20 +2888,19 @@ Session::cleanup_sources (CleanupReport& rep)
 					   in the region list.
 					*/
 					
-					std::string fpath = i->second->name ();
-
 					RegionFactory::remove_regions_using_source (i->second);
-					sources.erase (i);
 					
 					// also remove source from all_sources
 					
 					for (set<string>::iterator j = all_sources.begin(); j != all_sources.end(); ++j) {
 						spath = Glib::path_get_basename (*j);
-						if ( spath == fpath ) {
+						if (spath == i->second->name()) {
 							all_sources.erase (j);
 							break;
 						}
 					}
+
+					sources.erase (i);
 				}
 			}
 		}