Values in non-default polymorphic ports in graph toolkit are not serialized

Steps to reproduce:

1. Create and open a new project
2. Import the 'PolyPortsQAGraph.cs' script into the project
3. Create a new graph in 'Tools -> Graph Toolkit -> Create Polymorphic Ports QA Graph'
4. In the two displayed nodes (PolyNode and PolyNodeOpposite), set the 'in2' ports to the second available type (PolyNode -> String, PolyNodeOpposite -> Bool)
5. Set identical values in both nodes (Bool = 'true', String = "test")
6. Save the graph and close the window
7. Reopen the graph
8. Observe the values of each node

Actual results: PolyNode string is blank, PolyNodeOpposite bool is 'false'

Expected results: PolyNode string reads "test", PolyNodeOpposite bool reads 'true'

Reproducible with versions: 6000.7.0b1, 7000.0.0a1

Can’t test with versions: 6000.0.84f1 - 6000.7.0a6 (Polymorphic ports are not supported)

Tested on (OS): Windows 11 Pro (25H2)

Notes:

• Ports with default types are unaffected - their values are serialized correctly every time