Fix warning related to potential retain cycle
Fix warning related to potential retain cycle

Weakifying self removes the warning, but it's not clear
why the warning occurs here but does not seem to occur
in other equivalent methods where self is captured.

cloudmine/CloudMineSDK-iOS,cloudmine/CloudMineSDK-iOS,cloudmine/cloudmine-ios,apbendi/cloudmine-ios,apbendi/cloudmine-ios,cloudmine/cloudmine-ios,apbendi/cloudmine-ios,cloudmine/CloudMineSDK-iOS,cloudmine/cloudmine-ios