Unhandled exception: when saving file

* Description: [Enter what you did and what happened]
* Version: 0.1.6
* OS: Windows-10-10.0.17134-SP0
* Type: ``
* Value: 'NoneType' object has no attribute 'seek'
* Traceback:
```
File "D:\Repo\FakemonCreator\creator\mainwindow.py", line 196, in save
self._save()
File "D:\Repo\FakemonCreator\creator\mainwindow.py", line 184, in _save
self.data.save()
File "D:\Repo\FakemonCreator\creator\data\__init__.py", line 126, in save
self.container.add("data.json", data)
File "D:\Repo\FakemonCreator\creator\data\container.py", line 68, in add
if path in [x.filename for x in zipfile.ZipFile(self.__DATA).filelist]:
File "C:\Users\Jerakin\AppData\Local\Programs\Python\Python37-32\lib\zipfile.py", line 1200, in __init__
self._RealGetContents()
File "C:\Users\Jerakin\AppData\Local\Programs\Python\Python37-32\lib\zipfile.py", line 1263, in _RealGetContents
endrec = _EndRecData(fp)
File "C:\Users\Jerakin\AppData\Local\Programs\Python\Python37-32\lib\zipfile.py", line 236, in _EndRecData
fpin.seek(0, 2)

```