Fix ManagedDictionary error on null object

Source/Engine/Scripting/Internal/ManagedDictionary.h

@@ -53,7 +53,9 @@ struct FLAXENGINE_API ManagedDictionary
         Dictionary<KeyType, ValueType> result;
         const ManagedDictionary wrapper(managed);
         MArray* managedKeys = wrapper.GetKeys();
-        int32 length = managedKeys ? MCore::Array::GetLength(managedKeys) : 0;
+        if (managedKeys == nullptr)
+            return result;
+        int32 length = MCore::Array::GetLength(managedKeys);
         Array<KeyType> keys;
         keys.Resize(length);
         result.EnsureCapacity(length);

Source/Engine/Scripting/Scripting.cs

@@ -205,6 +205,8 @@ namespace FlaxEngine
 
         internal static object[] GetDictionaryKeys(IDictionary dictionary)
         {
+            if (dictionary == null)
+                return null;
             var keys = dictionary.Keys;
             var result = new object[keys.Count];
             keys.CopyTo(result, 0);