fix(clerk-js): Add explicit check for withSignUp being false (clerk#5286)

Author: alexcarpenter

.changeset/serious-mice-approve.md

@@ -0,0 +1,5 @@
+---
+'@clerk/clerk-js': patch
+---
+
+When a user passes `withSignUp={false}` we should opt out of combined flow even when `signUpUrl` is undefined.

packages/clerk-js/src/ui/contexts/components/SignIn.ts

@@ -45,7 +45,8 @@ export const useSignInContext = (): SignInContextType => {
 
   const isCombinedFlow =
     (signUpMode !== 'restricted' &&
-      Boolean(!options.signUpUrl && options.signInUrl && !isAbsoluteUrl(options.signInUrl))) ||
+      Boolean(!options.signUpUrl && options.signInUrl && !isAbsoluteUrl(options.signInUrl)) &&
+      context.withSignUp !== false) ||
     context.withSignUp ||
     false;