message: fix(typegoose): remove "non-null" assertion from "buildSchema"
diff: @@ -121,25 +121,25 @@ export function getModelWithString<U extends AnyParamConstructor<any>>(key: stri
  * const NameModel = mongoose.model("Name", NameSchema);
  * ```
  */
  -export function buildSchema<U extends AnyParamConstructor<any>>(cl: U, options?: mongoose.SchemaOptions) {
  +export function buildSchema<U extends AnyParamConstructor<any>>(cl: U, options?: mongoose.SchemaOptions): mongoose.Schema<U> {
  assertionIsClass(cl);
  logger.debug('buildSchema called for "%s"', getName(cl));
  const mergedOptions = mergeSchemaOptions(options, cl);
  - let sch: mongoose.Schema<U>;
  + let sch: mongoose.Schema<U> | undefined = undefined;
  /** Parent Constructor */
  let parentCtor = Object.getPrototypeOf(cl.prototype).constructor;
  // iterate trough all parents
  while (parentCtor?.name !== 'Object') {
  // extend schema
  - sch = _buildSchema(parentCtor, sch!, mergedOptions, false);
  + sch = _buildSchema(parentCtor, sch, mergedOptions, false);
  // set next parent
  parentCtor = Object.getPrototypeOf(parentCtor.prototype).constructor;
  }
  // get schema of current model
  - sch = _buildSchema(cl, sch!, mergedOptions);
  + sch = _buildSchema(cl, sch, mergedOptions);
  return sch;
  }
  