Do not draw indeterminite arc paths

fixes #62

Author: bsweeney

src/Svg/Tag/Path.php

@@ -451,7 +451,14 @@ function drawArc(SurfaceInterface $surface, $fx, $fy, $coords)
             array(),
         );
 
-        $segsNorm = $this->arcToSegments($tx - $fx, $ty - $fy, $rx, $ry, $large, $sweep, $rot);
+        $toX = $tx - $fx;
+        $toY = $ty - $fy;
+
+        if ($toX + $toY === 0) {
+            return;
+        }
+
+        $segsNorm = $this->arcToSegments($toX, $toY, $rx, $ry, $large, $sweep, $rot);
 
         for ($i = 0, $len = count($segsNorm); $i < $len; $i++) {
             $segs[$i][0] = $segsNorm[$i][0] + $fx;