Fix nil writing for optional RawRepresentable types

Author: pd95

Diff for: SwiftUIShim-Tests/SceneStorageTests.swift

@@ -459,10 +459,9 @@ class SceneStorageTests: XCTestCase {
         XCTAssertEqual(value.wrappedValue, newValue, "if set, the new value should be returned.")
         XCTAssertEqual(store.value(forKey: key) as? MyIntEnum.RawValue, newValue.rawValue, "the new value should be persisted session store")
 
-// FIXME: this is currently failing
-//        value.wrappedValue = nil
-//        XCTAssertEqual(value.wrappedValue, nil, "if set to nil, the value should be cleared.")
-//        XCTAssertEqual(store.value(forKey: key) as? MyIntEnum.RawValue, nil, "the nil value should be persisted session store")
+        value.wrappedValue = nil
+        XCTAssertEqual(value.wrappedValue, nil, "if set to nil, the value should be cleared.")
+        XCTAssertEqual(store.value(forKey: key) as? MyIntEnum.RawValue, nil, "the nil value should be persisted session store")
 
         store.set(externallySetValue.rawValue, forKey: key)
         XCTAssertEqual(value.wrappedValue, externallySetValue,

Diff for: SwiftUIShim/SceneStorage.swift

@@ -46,8 +46,11 @@ where T: RawRepresentable, T.RawValue: PropertyListTransform {
     }
 
     public static func writeValue(_ value: Any?, to store: inout [AnyHashable: Any], key: String) {
-        guard let value = value as? T? else { return }
-        store[key] = value?.rawValue
+        if value != nil, let value = value as? T? {
+            store[key] = value?.rawValue
+        } else {
+            store[key] = nil
+        }
     }
 }