Error with `HttpApp.toWebHandler` in version `^0.71`: TypeError: context.unsafeMap is not iterable

TypeError: context.unsafeMap is not iterable
    at unsafeMap (../../src/HttpApp.ts:169:25)
    at new Promise (<anonymous>)
    at eval (../../src/HttpApp.ts:164:6)
 ⨯ TypeError: context.unsafeMap is not iterable
    at unsafeMap (../../src/HttpApp.ts:169:25)
    at new Promise (<anonymous>)
    at eval (../../src/HttpApp.ts:164:6)