fix the hls bug

@@ -2120,6 +2120,11 @@ int SrsHttpServer::hls_update_ts(SrsRequest* r, string uri, string ts)
         }
     }
     
+    // find again, ignore if not exits.
+    if (shls.find(sid) == shls.end()) {
+        return ret;
+    }
+
     SrsHlsEntry* entry = shls[sid];
     srs_assert(entry);
     srs_assert(entry->tmpl);