hgweb: update _runwsgi try/except range to be valid

The `tmpl` variable is used in the `except` and `finally`, so we need it created
before the `try` is open.

mercurial/hgweb/hgwebdir_mod.py

@@ -410,7 +410,6 b' class hgwebdir:'
                     gc.collect(generation=1)
 
     def _runwsgi(self, req, res):
-        try:
             self.refresh()
 
             csp, nonce = cspvalues(self.ui)
@@ -419,6 +418,7 b' class hgwebdir:'
 
             virtual = req.dispatchpath.strip(b'/')
             tmpl = self.templater(req, nonce)
+        try:
             ctype = tmpl.render(b'mimetype', {b'encoding': encoding.encoding})
 
             # Global defaults. These can be overridden by any handler.