SDLShow initializer will crash if SDLMetadataType is nil

[joeljfischer]

Bug Report

If SDLShow initWithMainField1:(nullable NSString *)mainField1 mainField1Type:(nullable SDLMetadataType)mainField1Type mainField2:(nullable NSString *)mainField2 mainField2Type:(nullable SDLMetadataType)mainField2Type alignment:(nullable SDLTextAlignment)alignment is called with a nil mainField1(/2)Type, a crash will occur, even though those parameters are listed as nullable.

Reproduction Steps

1. Call initWithMainField1:(nullable NSString *)mainField1 mainField1Type:(nullable SDLMetadataType)mainField1Type mainField2:(nullable NSString *)mainField2 mainField2Type:(nullable SDLMetadataType)mainField2Type alignment:(nullable SDLTextAlignment)alignment with nil mainField1Type.

Expected Behavior

The method returns successfully without that parameter set

Observed Behavior

An exception crash occurs

OS & Version Information

• iOS Version: n/a
• SDL iOS Version: v5.3.0 WIP
• Testing Against: n/a