FAdd a minor fix for the b:plist_original_format;

[axrt]

Hi darfink!
First of all, thank you for the plugin, it is really useful.
I have encountered an issue with g:plist_original_format variable in the following context:
the autogroup in the plugin file calls plist#SetFiletype() and then checks if the file format is set to json. because i originally had it set to xml, i was receiving an error complaining about the b:plist_original_fromat not having been set. same with write..
This is introduced just a tiny fix for those situations; I would be ver glad if you choose to accept this pr.
Cheers,
axrt

[darfink]

Hi Axrt!

Thanks for your pull request, this seems like a very reasonable addition!
I'd would like to ask though, if there are any easy steps to recreate the issue you are describing so I can test it out myself?

[axrt]

Hi @darfink,
Sorry I got caught in mundane stuff and forgot.
So, eventually, the only setting I used to have was:

let g:plist_display_format = 'xml'
let g:plist_original_format = 'xml'

and then I was trying to open one of the .plist files on my mac (those are xmls). Please let me know if I can test anything else on my end for you.
Cheers