Properties are not type checked for propLines constant

[chaffneue]

in gentTypes.ts:

264:1 const propLines = Object.keys(def.properties).map(prop => {

def.properties can be undefined if there are no properties for a given object/stub.

which will throw an exception:

TypeError: Cannot convert undefined or null to object at Function.keys (<anonymous>) at renderTypeDoc (....\node_modules\openapi-client\dist\gen\js\genTypes.js:259:28)

json schema entry for repro

"myStubObject": { "title": "My Stub Object", "type": "object" },