merge method
Implementation
ZeroNavigationRailStyle merge(ZeroNavigationRailStyle? other) {
if (other == null) return this;
return copyWith(
backgroundColor: other.backgroundColor,
width: other.width,
activeColor: other.activeColor,
inactiveColor: other.inactiveColor,
indicatorColor: other.indicatorColor,
labelStyle: labelStyle?.merge(other.labelStyle) ?? other.labelStyle,
activeLabelStyle: activeLabelStyle?.merge(other.activeLabelStyle) ??
other.activeLabelStyle,
indicatorBorderRadius: other.indicatorBorderRadius,
);
}