Wt

With Wt (debug build of git 3.3.0-32-ga20ef3f), progressive enhancement sometimes fails with the Firebug debugger activated (and open). I've seen this with Firebug 1.11.4 in both Debian 7.1/Iceweasel 17.0.7 and Windows 7/Firefox 22. The error on the console is: TypeError: db is null intern...(line 304) if (db.addEventListener).

A similar issue is reported in Internet Explorer 10 with its builtin debugger activated (F12), although it happens with far less frequency. The error message in this case is: SCRIPT5007: Unable to get property 'addEventListener' of undefined or null reference.

This issue can be demonstrated with the attached test program, deployed at '/test' and configured for progressive mode. Visiting '/test' with the respective browser/debugger combinations, should hopefully reproduce the problem --- although it may take multiple attempts since the issue appears to be intermittent and timing related. The test program includes a setInternalPath() which causes Wt to issue a redirect. This seems to make the problem more reproducible, but I'm not sure that it is actually required.

This may be related to #1945, although that issue was easier to reproduce.

I've attached a patch that seems to help with the issue.