fix: divide by zero now does not crash

[xandrefreire]

Hello,

Thank you for this library.

Bug Fix: Division by Zero

I have identified a runtime crash issue caused by division by zero. For instance, the following code snippet causes the library to crash:

let rule =
"""
{ "/" : [10, 0] }
"""

// Example parsing
let result: String? = try? JSONLogicClient.applyRule(rule, to: nil)

print("result = \(String(describing: result))")

This pull request implements a fix to prevent this crash.

Additional Observations

1. Handling Nullable Operands in Arithmetic Operations:

There are similar crashes when operands are null. For example:

let rule =
"""
{ "/" : [10, null] }
"""

// Example parsing
let result: String? = try? JSONLogicClient.applyRule(rule, to: nil)

print("result = \(String(describing: result))")

This likely happens because null is treated as zero.

2. Logical Operations with or and null:

This is a valid expression and returns true:

let rule =
"""
{ "or" : [true, null] }
"""

// Example parsing
let result: String? = try? JSONLogicClient.applyRule(rule, to: nil)

print("result = \(String(describing: result))")

3. Logical Operations with and and null:

However, this expression returns nil:

let rule =
"""
{ "and" : [true, null] }
"""

// Example parsing
let result: String? = try? JSONLogicClient.applyRule(rule, to: nil)

print("result = \(String(describing: result))")

It would be beneficial to handle nullable operands more predictably.

Thank you for your time reviewing this pull request.

Best regards,

Alexandre