Fix missing error handling

lib/graphviz.js

@@ -26,12 +26,12 @@ exports.graph = function(id) {
  * @constructor
  * @param {String} id The graphID
  * @return {Graph}
- * @api public 
+ * @api public
  */
 exports.digraph = function(id) {
   var graph = new Graph(null, id);
   graph.type = 'digraph';
-  return graph;  
+  return graph;
 };
 
 function _parse(file, callback, errback) {
@@ -53,8 +53,8 @@ function _parse(file, callback, errback) {
   graphviz.stdin.end();
   graphviz.on('exit', function(code) {
     if(code !== 0 || __graph_eval === undefined) {
-      if(errback) { 
-        errback(code, out, err); 
+      if(errback) {
+        errback(code, out, err);
       }
     } else {
       callback(__graph_eval);
@@ -67,16 +67,26 @@ function _parse(file, callback, errback) {
  * @param {String} file_or_script The DOT script or file
  * @param {Function} callback
  * @param {Function} errback
- * @api public 
+ * @api public
  */
 exports.parse = function(file_or_script, callback, errback) {
   if(fsExt.exist(file_or_script)) {
     _parse(file_or_script, callback, errback);
   } else {
     temp.open('node-graphviz', function(err, info) {
-      fs.write(info.fd, file_or_script);
-      fs.close(info.fd, function(err) {
-        _parse(info.path, callback, errback);
+      if(err) {
+        return errback(err);
+      }
+      fs.write(info.fd, file_or_script, function(err) {
+        if(err) {
+          return errback(err);
+        }
+        fs.close(info.fd, function(err) {
+          if(err) {
+            return errback(err);
+          }
+          _parse(info.path, callback, errback);
+        });
       });
     });
   }