[Fabric] [iOS] Fix app crash when selecting an empty value

[bernhardoj]

Selecting an item with an empty value crashes the app because we convert an empty string to null,

picker/ios/RNCPickerComponentView.mm

Line 51 in 7b7a95f

dictItem[@"value"] = RCTNSStringFromStringNilIfEmpty(item.value);

and it crashes here.

picker/ios/RNCPicker.mm

Line 160 in 7b7a95f

.newValue = RCTStringFromNSString(RCTNullIfNil(_items[row][@"value"])),

Test

1. Run the example app with RCT_NEW_ARCH_ENABLED enabled
2. Add a picker item with an empty value to the example
3. Scroll the picker to select the item with an empty value

[Naturalclar]

LGTM!

[Naturalclar]

🎉 This PR is included in version 2.7.6 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[bernhardoj]

Great, thanks!