meta-app-framework: Handle html5 apps not having debug widgets

meta-app-framework: Handle html5 apps not having debug widgets

The previous aglwgt.bbclass change to make build/package errors fatal
now trips up on the HTML5 applications, as they do not produce a debug
widget, and the logic changes assumed that all widget builds would
have one.  To handle this, if there is no debug widget present when
doing do_install, check the config.xml file in the release widget and
do not throw an error if the widget type is "text/html".

Bug-AGL: SPEC-3593

Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Change-Id: If58c3065464d2d2ea3d78b8ce31304d00fae6504
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/25368
Tested-by: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-build: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-boot-test: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>