Don't fail on GBFS system id collisions we can't resolve

This can happen when feeds appear in the NABSA systems.csv that we also
have in our own feed list and both use different URLs that after version
discovery end up pointing to the same URL.

src/tools/gbfsprobe.cpp

@@ -181,9 +181,8 @@ void GBFSProbe::checkDuplicateSystemIds()
         }
     }
 
-    if (!m_gbfsFeeds.isEmpty()) {
-        assert(!m_syntheticSystemId);
-        qWarning() << "Feeds with colliding system ids:" << m_gbfsFeeds;
+    qWarning() << "Feeds with colliding system ids:" << m_gbfsFeeds.size() << m_gbfsFeeds;
+    if (!m_gbfsFeeds.isEmpty() && !m_syntheticSystemId) {
         m_syntheticSystemId = true;
         m_currentFeedIdx = -1;
         m_throttleTime = 0;