Fixed an issue with 32 bit devices (i.e. iPhone 4S).
Fixed an issue with 32 bit devices (i.e. iPhone 4S).

* Using `UInt(string) == nil` to check whether a string contains only numeric characters fails on 32 bit devices: entering a number of > 2^32 results in nil, even though it's still numeric. Instead use string operations for this.

prolificinteractive/Caishen,prolificinteractive/Caishen