fix: empty manufacturer lead to failed parse_device_properties

[clansty]

My tv returns empty with getprop ro.product.manufacturer

this leads the .strip() removed the empty line and properties will become only 4 lines. _parse_device_properties will stop parsing.

if android version is not parsed, the library will use wrong command to get state and control the device.

I added two echo % line in the begin and end of the "get properties" command to prevent empty manufacturer to be erased by strip