Prevent plugin from crashing when searching for non-existent trackId

[robinbanbury]

Description

When the user searches for a track, the track and playlist index are returned by findTrackById. If a suitable track is not found, use NSNull to represent the track, as the NSDictionary returned by this function cannot use 'nil' values.

Related Issue

14

Motivation and Context

Required to gracefully handle user / developer errors without crashing the plugin

How Has This Been Tested?

Before and after test on a live device with multiple tracks

Screenshots (if appropriate):

None appropriate, but logs before:

2018-08-15 12:56:33.947454+0100 GigLicker[9622:3395198] New playlist set
2018-08-15 12:56:33.947509+0100 GigLicker[9622:3395198] RmxAudioPlayer.execute=playTrackById, 1234567890
2018-08-15 12:56:33.948641+0100 GigLicker[9622:3395198] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSPlaceholderDictionary initWithObjects:forKeys:count:]: attempt to insert nil object from objects[0]'
*** First throw call stack:
(0x183566d8c 0x1827205ec 0x1834ff750 0x1834380cc 0x183437f48 0x1030991a4 0x10308fd70 0x1030ae904 0x102f542bc 0x102f54120 0x102f55d9c 0x193273a2c 0x193210734 0x1932128a4 0x192f79d18 0x1931b920c 0x192f3ccfc 0x192f3f704 0x18ab9e17c 0x18ab9e3ec 0x18350f404 0x18350ec2c 0x18350c79c 0x18342cda8 0x185412020 0x18d44c758 0x102f496ec 0x182ebdfc0)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb) frame variable
(RmxAudioPlayer *) self = 0x00000001c00d6ff0
(SEL) _cmd = "findTrackById:"
(__NSCFString *) trackId = 0x00000001c42379e0 @"1234567890"
(NSInteger) idx = -1
(AudioTrack *) track = nil

Logs after:

2018-08-15 13:19:22.497923+0100 GigLicker[9630:3403120] New playlist set
2018-08-15 13:19:22.544611+0100 GigLicker[9630:3403120] RmxAudioPlayer.execute=playTrackById, 1234567890
2018-08-15 13:19:22.586266+0100 GigLicker[9630:3403120] WARN: Track ID not found

And the player does not start playing - suitable since there is no corresponding track to play for this selection.

Types of changes

• [x] Bug fix
• [ ] New feature
• [ ] Breaking change

Checklist:

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.

[robinbanbury]

@codinronan any chance this can be reviewed?

[codinronan]

Hi @robincsmith sorry about that I've been a bit overwhelmed lately!!

[robinbanbury]

No worries pal, it sounds like you've been very busy - it happens to the best of us! :-D

Cheers for merging the fixes, and for the excellent work on the plugin - it's super useful.