[TIMOB-14567] Android: Setting "color" to null on Label causes color to be transparent

problem

When setting the *color* property of a Ti.UI.Label to *null* it makes the color transparent on Android. On iOS and Mobileweb the color is returned to the default black (#000). While the default color can be determined by the underlying platform, it should be a visible color to give parity across the platforms. In others words, setting *color* to null should either make the color transparent on all platforms, or a solid color on all platforms.

expected

When I set the the *color* property of a Ti.UI.Label to *null*, I expect the behavior, whether it makes the Label transparent or a solid color, to be the same on all platforms.

test case

app.js

var win = Ti.UI.createWindow({
	backgroundColor: '#fff',
	modal: false,
	exitOnClose: true
});
var label = Ti.UI.createLabel({
	text: 'just a test label'
});
label.addEventListener('click', function(e) {
	label.color = null;
});

win.add(label);
win.open();