Fixed incorrect parameter name

Author: mattglover

Classes/ios/UISlider+FlatUI.m

@@ -35,7 +35,7 @@ - (void) configureFlatSliderWithTrackColor:(UIColor *)trackColor
     [self setMinimumTrackImage:progressImage forState:UIControlStateNormal];
     [self setMaximumTrackImage:trackImage forState:UIControlStateNormal];
 
-    UIImage *normalSliderImage = [UIImage circularImageWithColor:thumbColor size:CGSizeMake(24, 24)];
+    UIImage *normalSliderImage = [UIImage circularImageWithColor:thumbColorNormal size:CGSizeMake(24, 24)];
     [self setThumbImage:normalSliderImage forState:UIControlStateNormal];
 
     UIImage *highlighedSliderImage = [UIImage circularImageWithColor:highlightedThumbColor size:CGSizeMake(24, 24)];