Stack overflow when comparing two nil objects of type [String: Any]?

[AlexWoodblock]

Describe the bug
Extension that overrides == operator for Optional<[String:Any]> causes infinite loop with stack overflow when comparing two nil optionals of this type.

To reproduce

1. Add LaunchDarkly 4.0 to Podfile:
   pod 'LaunchDarkly', '~>4.0.0'
2. Run pod install
3. Add following code anywhere in application

let dict1: [String: Any]? = nil
let dict2: [String: Any]? = nil

if dict1 == dict2 {
    print("This will never be printed")
}

4. Run the application and make sure the code executes.
5. Application will crash due to stack overflow because of line 79 in LaunchDarkly/Extensions/Dictionary.swift - it enters recursive loop in case of lhs and rhs both being nil.

Expected behavior
== should return true for comparison of two nil [String:Any]?objects.

SDK version
4.0.0

Language version, developer tools
Swift 5

OS/platform
iOS 12

[torchhound]

I just released iOS client 4.1.2 with your fix for this issue, thanks again for the PR!

[lietusme]

Created similar issue #197