Fix another case of potential overload ambiguity.

Apply the same fix that went into
d9cdc7e to another location.

After an upcoming type checker change the previous code would be
considered ambiguous.

Author: rudkx

Foundation/NSCFDictionary.swift

@@ -39,7 +39,7 @@ internal final class _NSCFDictionary : NSMutableDictionary {
     override func object(forKey aKey: Any) -> Any? {
         let value = CFDictionaryGetValue(_cfObject, unsafeBitCast(_SwiftValue.store(aKey), to: UnsafeRawPointer.self))
         if value != nil {
-            return _SwiftValue.fetch(unsafeBitCast(value, to: AnyObject.self))
+            return _SwiftValue.fetch(unsafeBitCast(value, to: AnyObject.self) as AnyObject?)
         } else {
             return nil
         }