config: fix restoreconfig of non existing config
When the section, but no value existed, the `del` call raised a key error.
--- a/mercurial/config.py Thu Jul 31 13:51:17 2014 -0700
+++ b/mercurial/config.py Tue Aug 05 21:16:24 2014 -0700
@@ -76,7 +76,7 @@
# no data before, remove everything
section, item = data
if section in self._data:
- del self._data[section][item]
+ self._data[section].pop(item, None)
self._source.pop((section, item), None)
def parse(self, src, data, sections=None, remap=None, include=None):