SANE genesys backend causes lockup during sane_get_devices

[goncalomb]

The genesys backend (http://www.sane-project.org/sane-backends.html#S-GENESYS) is used by a fair number of devices, so it would be good to find the issue that is causing it to lock during sane_get_devices, and re-enable the backend.

sane-wasm/build.sh

Lines 126 to 136 in 2d11481

	# The backends are selected automatically by reading SANE's .desc files and
	# selecting the backends that support at least one USB device.
	# http://www.sane-project.org/sane-backends.html
	# Extra backends:
	# test: for testing
	# gphoto2,v4l: not enabled ATM, XXX: check compatibility and usefulness
	# Excluded backends:
	# template,unsupported: not real backends
	# dell1600n_net: doesn't really support any USB device
	# genesys: causes lockup during sane_get_devices, XXX: to be fixed
	SANE_WASM_BACKENDS=$(./utils.py usb-backends -i test -e template,unsupported,dell1600n_net,genesys)

Can be debugged using the test page, by stopping script execution right after sane_get_devices. But can cause the inspector to lock and crash.