If an add-on folder contains only number, but does not contains a
meta.json file, or if this file does not contains a "mod" value, then
the following uninformative message error occur:
```Python
File "aqt/addons.py", line 387, in onCheckForUpdates
File "aqt/addons.py", line 183, in checkForUpdates
File "aqt/addons.py", line 199, in _updatedIds
<class 'TypeError'>: '<' not supported between instances of 'NoneType' and 'int'
```
This is because there is a .get in a code while the None value makes
no sens. Thus, I replaced None by a 0 value. Which ensure that, if the
last modification time is missing, the update will be done. Three case
may occur:
* either the addon is already up to date, and it's only a waste of
bandwidth
* either the add-on is not up to date, and updating was the initial
goal anyway
* Or some change did occur in the add-on folder (which is actually
probably, since it would explain the "missing mod problem"; in this
case this change may be lost, but thout would be the same problem
if the mod number was still there.
Other solutions which I could implement would be:
* asking for the user whether they want to update
* considering that it's not an ankiweb related add-on anymore, and
ignore it.
Since we're automatically disabling proxies now, the main remaining
issue seems to be Windows users resuming their machine from sleep -
for some reason localhost is inaccessible during the resume process.
The removal of this function in #270 causes <br> to remain in seemingly
empty editor fields, which in turn wrongly prompts the "Close and lose
current input?" dialog.
ideally the original code should be correctly cleaning up the hooks,
but if it does not, then we don't want to repeatedly present the user
with confusing errors when they try to check their database is ok.
if an error occurred after QDialog.accept() had been called,
the hook was left lying around and caused errors when reset later
fired
File "aqt\main.py", line 1028, in onCheckDB
File "aqt\main.py", line 516, in reset
File "anki\hooks.py", line 28, in runHook
File "aqt\modelchooser.py", line 47, in onReset
File "aqt\modelchooser.py", line 82, in updateModels
<class 'RuntimeError'>: wrapped C/C++ object of type QPushButton has been deleted
