On any activity recreation with saved state (config changes such as
night mode), the FragmentManager restores the Permissions fragment
reflectively and requires a no-arg constructor; it only had
Permissions(View), so the activity failed to start with
Fragment$InstantiationException.
Also regenerate cmd/pad/Permissions.jar from the .java source in both
build scripts: gogio does not compile the app's own .java files - it
silently merges any *.jar in the Go package dirs into the dex, so the
stale Aug-16 jar shadowed source edits (which is how this bug went
unnoticed).
This crash is separate from the black-screen hang after relaunch,
which is fixed in the gioui fork (app/os_android.go: skip the window
handshake ack on re-attach).
