BinaryExporter fails when serializing multiple UserData objects containing lists

I was playing around with @copilot and it says it found this issue: https://github.com/jMonkeyEngine/jmonkeyengine/pull/2607#issuecomment-3887504117

Reporting here for tracking, but i haven't validated it yet.

When a Spatial has multiple UserData entries containing lists (e.g., "int-list", "string-list", "float-list"), the BinaryExporter/BinaryImporter fails to deserialize correctly. The first list in the userData HashMap deserializes successfully, but subsequent lists return null and cause an ArrayIndexOutOfBoundsException during deserialization.

Steps to reproduce:

1. Set testLists=true in jme3-plugins/src/test/java/com/jme3/export/JmeExporterTest.java (line 142)
2. Run ./gradlew :jme3-plugins:test --tests "com.jme3.export.JmeExporterTest"
3. Observe that BinaryImporter (Node 1) returns null for int-list and string-list, while float-list works (being first in iteration order)

Error:

java.lang.ArrayIndexOutOfBoundsException: Index -3 out of bounds for length 4
    at com.jme3.export.binary.ByteUtils.rightAlignBytes(ByteUtils.java:554)
    at com.jme3.export.binary.BinaryInputCapsule.readInt(BinaryInputCapsule.java:834)
    at com.jme3.export.binary.BinaryInputCapsule.setContent(BinaryInputCapsule.java:154)

Notes:

• XMLExporter/XMLImporter works correctly with all lists
• Only affects BinaryExporter when multiple UserData objects with lists exist
• Appears to be a byte stream alignment issue in the binary format