[TIMOB-23778] iOS: Improve warning when calling iOS10 visual effects for Ti.UI.iOS.BlurView on < iOS10

[ERROR] Invalid type passed to function. expected: Number, was: NSNull -[TiUIiOSBlurView setEffect_:] (TiUIiOSBlurView.m:43)

var win = Ti.UI.createWindow({
    backgroundColor: "#fff"
});
 
// Reference image (or view)
var img = Ti.UI.createImageView({
    image: "/default_app_logo.png",
    top: 100,
    width: 300,
    height: 300
});
 
// Blur view
var blur = Ti.UI.iOS.createBlurView({
    width: Ti.UI.FILL,
    height: Ti.UI.FILL
});
 
img.add(blur);
 
// Effect controls
var tabs = Ti.UI.iOS.createTabbedBar({
    labels: ["Extra light", "Light", "Dark", "Regular", "Prominent"],
    bottom: 100
});
 
// Available blur effects
var effects = [
    Ti.UI.iOS.BLUR_EFFECT_STYLE_EXTRA_LIGHT,
    Ti.UI.iOS.BLUR_EFFECT_STYLE_LIGHT,
    Ti.UI.iOS.BLUR_EFFECT_STYLE_DARK,
    Ti.UI.iOS.BLUR_EFFECT_STYLE_REGULAR,
    Ti.UI.iOS.BLUR_EFFECT_STYLE_PROMINENT
];
 
tabs.addEventListener("click", function(e) {
    blur.setEffect(effects[e.index]);
});
 
win.add(tabs);
win.add(img);
win.open();