[Bug]: tsp-openapi3 crashes for requestBody with $ref

[TomerAberbach]

Describe the bug

Referencing a requestBody via a $ref to #/components/requestBodies causes a crash in tsp-openapi3.

Reproduction

example.yml:

openapi: 3.0.0
info:
  title: (title)
  version: 0.0.0
paths:
  /thing:
    post:
      operationId: createThing
      requestBody:
        $ref: '#/components/requestBodies/RequestBody'
components:
  requestBodies:
    RequestBody:
      content:
        application/json:
           type: object

tsp-openapi3 example.yml --output-dir ./tsp-output

Result:

TypeError: Cannot convert undefined or null to object
    at Function.keys (<anonymous>)
    at transformRequestBodies (file:///Users/tomeraberbach/Downloads/test/node_modules/.pnpm/@[email protected]_patch_hash=qfvurrzg7d2mskofobmxri2twe_@[email protected]_@ty_y2vkd7p4rkeieiph4t7ptycfkm/node_modules/@typespec/openapi3/dist/src/cli/actions/convert/transforms/transform-paths.js:84:38)
    at transformPaths (file:///Users/tomeraberbach/Downloads/test/node_modules/.pnpm/@[email protected]_patch_hash=qfvurrzg7d2mskofobmxri2twe_@[email protected]_@ty_y2vkd7p4rkeieiph4t7ptycfkm/node_modules/@typespec/openapi3/dist/src/cli/actions/convert/transforms/transform-paths.js:40:32)
    at transform (file:///Users/tomeraberbach/Downloads/test/node_modules/.pnpm/@[email protected]_patch_hash=qfvurrzg7d2mskofobmxri2twe_@[email protected]_@ty_y2vkd7p4rkeieiph4t7ptycfkm/node_modules/@typespec/openapi3/dist/src/cli/actions/convert/transforms/transforms.js:9:24)
    at convertAction (file:///Users/tomeraberbach/Downloads/test/node_modules/.pnpm/@[email protected]_patch_hash=qfvurrzg7d2mskofobmxri2twe_@[email protected]_@ty_y2vkd7p4rkeieiph4t7ptycfkm/node_modules/@typespec/openapi3/dist/src/cli/actions/convert/convert-file.js:12:21)

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