Fix a crash on keyboard event in PostComment
Fix a crash on keyboard event in PostComment

There was a specific condition where a keyboard event would cause
a crash in PostComment after a low memory warning / viewDidUnload

[Deliver #27952201]

dontfallisleep/socialize-sdk-ios,socialize/socialize-sdk-ios,dontfallisleep/socialize-sdk-ios,socialize/socialize-sdk-ios,dontfallisleep/socialize-sdk-ios,socialize/socialize-sdk-ios,socialize/socialize-sdk-ios,dontfallisleep/socialize-sdk-ios,dontfallisleep/socialize-sdk-ios,socialize/socialize-sdk-ios,socialize/socialize-sdk-ios,dontfallisleep/socialize-sdk-ios