fix bug when using UIColor presets

There was a bug that in some cases could have glClearColor set to undefined value.

The cause of this bug is the method

+ (void)getColorComponentsFromCGColor:(CGColorRef)color
                                  red:(CGFloat *)red
                                green:(CGFloat *)green
                                 blue:(CGFloat *)blue
                                alpha:(CGFloat *)alpha

That supposed the CGColorSpaceRef returned by the UIColor was always kCGColorSpaceGenericRGB (see below)

- (void)setBackgroundColor:(id)backgroundColor
{
    _backgroundColor = backgroundColor;
    if (backgroundColor)
    {
        CGColorRef colorRef = [backgroundColor CGColor];
        CGFloat red; CGFloat green; CGFloat blue; CGFloat alpha;
        [EZAudioUtilities getColorComponentsFromCGColor:colorRef
                                                    red:&red
                                                  green:&green
                                                   blue:&blue
                                                  alpha:&alpha];
        //
        // Note! If you set the alpha to be 0 on mac for a transparent view
        // the EZAudioPlotGL will make the superview layer-backed to make
        // sure there is a surface to display itself on (or else you will get
        // some pretty weird drawing glitches
        //
#if !TARGET_OS_IPHONE
        if (alpha == 0.0f)
        {
            [self.superview setWantsLayer:YES];
        }
#endif
        glClearColor(red, green, blue, alpha);
    }
    else
    {
        glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
    }
}

Notice that's not true when you pass as UIColor things like [UIColor whiteColor]