Fixed player instance deprecating.

[az33zy]

Deactivating an audio session that has running I/O. All I/O should be stopped or paused prior to deactivating the audio session.

[saiday]

Hi @cybitzix, after you set AVAudioSession's category to nil, what would category property would be if you access it by [[AVAudioSession sharedInstance] category]?

[az33zy]

Hi. Do I need accessing category property after I deprecate the instance?

[saiday]

No no, I am wondering about setting category to nil, from Apple's document I don't see category can be set to nil, so just a little curious what will category be after set to nil.

[az33zy]

I had an error with deprecating player instance in iOS 8 and found a solution. To completely stop I/O in an audio session we need to set the category property to nil.

[sgtsquiggs]

This is causing an error in iOS9

- (BOOL)setCategory:(NSString * nonnull)theCategory error:(NSError * nullable * nullable)outError

Category shouldn't be set to 'nil'.

[saiday]

@sgtsquiggs thank you for reporting this issue, reverting this pull request.
@cybitzix FYI.

[saiday]

@cybitzix I run HysteriaPlayer on iOS 8 as well, I have no errors when deprecating. Can you paste the error you got here, so we can tracking.