download_factory: don't check for "removed-right-after-add" when load…

…ing session

As no command is attached when loading from session, it is
impossible for this edge case to occur.

"find" on the download list, a "std::list" linked list, is
an O(n) operation. With it, the session loading is O(n^2),
where n is the number of entities in the session directory.

As such, remove this unnecessary check to speed things up.

src/core/download_factory.cc

@@ -352,13 +352,15 @@ DownloadFactory::receive_success() {
       rpc::parse_command_multiple_std(command, rpc::make_target(download));
     }
 
-    if (m_manager->download_list()->find(infohash) ==
-        m_manager->download_list()->end())
-      throw torrent::input_error("The newly created download was removed.");
+    if (!m_session) {
+      if (m_manager->download_list()->find(infohash) ==
+          m_manager->download_list()->end()) {
+        throw torrent::input_error("The newly created download was removed.");
+      }
 
-    if (!m_session)
       rpc::call_command(
         "d.state.set", (int64_t)m_start, rpc::make_target(download));
+    }
 
     rpc::commands.call_catch(m_session ? "event.download.inserted_session"
                                        : "event.download.inserted_new",