Certain schemas can cause unhandled undefined in Formly JSON parser

[camden-penn]

Description

Came to light in discussion of issue #2875. Schemas such as

{
  "type": "object",
  "properties":{
    "prop":{
      "type":"array"
    }
  }
}

cause the parser to call FormlyJsonschema.resolveSchema(schema, options) with schema set to the unexpected value undefined. This function is not hardened against such a possibility, and errors out before the schema can be parsed.

Minimal Reproduction

https://stackblitz.com/edit/extended-formly-config-does-not-intercede?file=src%2Fapp%2Fapp.component.ts

Your Environment

• Angular version: 8.2.14
• Formly version: 5.10.20

[aitboudad]

This issue has been fixed and released as part of v5.10.22 release.

Please let us know, in case you are still encountering a similar issue/problem.
Thank you!