Many crashes with SIGABRT when receive Metadata

[Sergionius]

Hi i use LGAudioStreamMetadataGetter to get metadata from several stream, but sometime my app crashes with message: "malloc: *** error for object double free" in https://github.com/Friend-LGA/LGAudioStreamHelper/blob/master/LGAudioStreamHelper/LGAudioStreamMetadataGetter/LGAudioStreamMetadataGetter.m#L158
may be its something multi-threading