BugreportManager takes screenshot even though screenshotFd is null

Bug: 385709501
Fix: 385709501
Flag: android.os.bugreport_deferred_consent_screenshot_fix
Test: tested on a device
(cherry picked from https://partner-android-review.googlesource.com/q/commit:1de4dc9d0db76cf6f914e38af0a7af91cda58cdc)
Merged-In: Ib1b90701312096ecdacad91b4d9e44ca184a12db
Change-Id: Ib1b90701312096ecdacad91b4d9e44ca184a12db