fix(v0): validation was crashing when a conditional reaches into a undefined fieldset value

[sandrina-p]

What

V0 crashes when a schema conditional reaches into a nested fieldset whose value is null/undefined. This happens for rows/payloads that omit a fieldset, throwing instead of validating.

Example

Schema with a conditional that reaches into the pet fieldset:

{
  "type": "object",
  "properties": {
    "pet": {
      "type": "object",
      "x-jsf-presentation": { "inputType": "fieldset" },
      "properties": {
        "species": { "type": "string", "enum": ["dog", "cat"] }
      }
    },
    "pet_name": { "type": "string" }
  },
  "allOf": [
    {
      "if": {
        "properties": {
          "pet": { "properties": { "species": { "const": "dog" } } }
        },
        "required": ["pet"]
      },
      "then": { "required": ["pet_name"] }
    }
  ]
}

Validating a value that omits the fieldset crashes:

form.handleValidation({ pet: null }) // TypeError: Cannot read properties of null (reading 'species')

Root cause

checkIfConditionMatchesProperties recurses into the fieldset with formValues["pet"] which has a null value, so then it crashes inside.

Fix

Coalesce to {} (formValues[name] ?? {}) so the nested condition evaluates instead of crashing.

REF CPF-3408.

🤖 co-written with Claude Code