don't try to run a non-existent file

lib/index.js

@@ -133,6 +133,15 @@ function pausingRepl(fn) {
 }
 
 function runFile(filename, callback) {
+    // check if file exists. might not have been saved.
+    try {
+        fs.statSync(filename)
+    } catch (e) {
+        _repl.stream.write('nothing to run\n')
+        callback()
+        return
+    }
+    
     var Script = process.binding('evals').Script
       , evalcx = Script.runInContext
       , read = fs.createReadStream(filename)