Fix a bug: when `leftPadding` is not set, the app crashes.
Fix a bug: when `leftPadding` is not set, the app crashes.

JakeLin/IBAnimatable,seanwoodward/IBAnimatable,IBAnimatable/IBAnimatable,JakeLin/IBAnimatable,IBAnimatable/IBAnimatable,alexiosdev/IBAnimatable,alexiosdev/IBAnimatable,seanwoodward/IBAnimatable,IBAnimatable/IBAnimatable