ensure progress window cleared if error on add-on import

aqt/addons.py

@@ -240,6 +240,7 @@ Are you sure you want to continue?"""
         log = []
         errs = []
         self.mw.progress.start(immediate=True)
+        try:
             for path in paths:
                 base = os.path.basename(path)
                 ret = self.install(path)
@@ -254,6 +255,7 @@ Are you sure you want to continue?"""
                                   % dict(base=base, error=msg)))
                 else:
                     log.append(_("Installed %(name)s" % dict(name=ret[1])))
+        finally:
             self.mw.progress.finish()
         return log, errs