androidvideo: use the actual minimum video resolution instead of 2x2

The method for checking the maximum resolution is now also used to check the minimum resolution.

This change fixes so that the application doesn't crash if no video dimensions are given, but the minimum size will still be used  by default.
Why don't you use GST_DEBUG() and friends here? It is assumed that there is proper GStreamer debug -> Android logs handling in Android apps that use GStreamer. Would make these macros a bit simpler and add more information to the output automatically.