Fix #573

Author: robocoder

src/Compiler.php

@@ -2699,7 +2699,9 @@ public function compileValue($value)
                 $b = round($b);
 
                 if (count($value) === 5 && $value[4] !== 1) { // rgba
-                    return 'rgba(' . $r . ', ' . $g . ', ' . $b . ', ' . $value[4] . ')';
+                    $a = new Node\Number($value[4]);
+
+                    return 'rgba(' . $r . ', ' . $g . ', ' . $b . ', ' . $a . ')';
                 }
 
                 $h = sprintf('#%02x%02x%02x', $r, $g, $b);
@@ -4336,7 +4338,7 @@ protected function libRgb($args)
     protected function libRgba($args)
     {
         if ($color = $this->coerceColor($args[0])) {
-            $num = ! isset($args[1]) ? $args[3] : $args[1];
+            $num = isset($args[3]) ? $args[3] : $args[1];
             $alpha = $this->assertNumber($num);
             $color[4] = $alpha;