fix: nil dynamic config refresh crash (#288) (#289)
fix: nil dynamic config refresh crash (#288) (#289)

Abort execution of completion block after dynamic config refresh completes if self is now nil

Co-authored-by: Jamie Altreuter <b4dde37aa2aac745c0e6c43447507eaeace3e59f@aisense.com>
amplitude/Amplitude-iOS,amplitude/Amplitude-iOS,amplitude/Amplitude-iOS,amplitude/Amplitude-iOS