/// Returns the value of a variable if it is not null,
/// otherwise returns the fallback value.
/// @param {Any} $var - The variable to check.
/// @param {Any} $fallback - The fallback value.
/// @return {Any} - The value of the variable or the fallback value.
///
/// @example scss - Usage
///   $foo: null;
///   @debug k-if-var( $foo, "bar" ); // => "bar"
///   $foo: "baz";
///   @debug k-if-var( $foo, "bar" ); // => "baz"
@function k-if-var( $var, $fallback ) {
    @return if( $var != null, $var, $fallback );
}