Fix Response.statusText

[tkrotoff]

Inside Response constructor, this line:
this.statusText = 'statusText' in options ? options.statusText : '' is incorrect and should be:
this.statusText = options.statusText === undefined ? '' : '' + options.statusText

With Firefox 84, Chrome 88, WebKit 605.1.15 native Response gives:

• new Response('').statusText ==> ""
• new Response('', {statusText: undefined}).statusText ==> ""
• new Response('', {statusText: null}).statusText ==> "null" (yes a string)
• new Response('', {statusText: ''}).statusText ==> ""
• new Response('', {statusText: 'hello'}).statusText ==> "hello"
• new Response('', {statusText: 0}).statusText ==> '0'
• new Response('', {statusText: 1}).statusText ==> '1'

Screenshots

With whatwg-fetch 3.0.5 you get:

• new Response('').statusText ==> "" ==> OK
• new Response('', {statusText: undefined}).statusText ==> undefined ==> KO (should be "")
• new Response('', {statusText: null}).statusText ==> null ==> KO (should be a string)
• new Response('', {statusText: ''}).statusText ==> "" ==> OK
• new Response('', {statusText: 'hello'}).statusText ==> "hello" ==> OK
• new Response('', {statusText: 0}).statusText ==> 0 ==> KO (should be a string)
• new Response('', {statusText: 1}).statusText ==> 1 ==> KO (should be a string)

[JakeChampion]

This is released in v3.6.0 -- https://github.com/github/fetch/releases/tag/v3.6.0