Fix for when missing keys in returned data

[greenthegarden]

Hi Simon. I have made a fork of the project at https://github.com/greenthegarden/asx_sensor to resolve an issue I encountered when keys were missing from the returned json object. I encountered the issue and have tested the fix when getting prices for company 'Endeavour Group Ltd - EDV`.

[simonhq]

Hey green,

Looks good, did you want to raise a pull request?

Simon.