fix #913 improve log message

src/main/java/org/codelibs/fess/app/web/go/GoAction.java

@@ -141,7 +141,7 @@ public class GoAction extends FessSearchAction {
                     }
                     return response;
                 } catch (final Exception e) {
-                    logger.debug("Failed to load: " + doc, e);
+                    logger.warn("Failed to load: " + doc, e);
                     saveError(messages -> messages.addErrorsNotLoadFromServer(GLOBAL, targetUrl));
                     return redirect(ErrorAction.class);
                 }