only unref timers if unref is available

Fix #374

Author: isaacs

lib/base.js

@@ -73,7 +73,8 @@ Base.prototype.setTimeout = function (n) {
   } else {
     this.start = Date.now()
     this.timer = setTimeout(this.timeout.bind(this), n)
-    this.timer.unref()
+    if (this.timer.unref)
+      this.timer.unref()
   }
 }
 

lib/spawn.js

@@ -135,5 +135,6 @@ Spawn.prototype.timeout = function (extra) {
       this.proc.kill('SIGKILL')
     }
   }.bind(this), 1000)
-  t.unref()
+  if (t.unref)
+    t.unref()
 }