Avoid calling done() twice.

Author: lrowe

lib/runnable.js

@@ -324,8 +324,11 @@ Runnable.prototype.run = function (fn) {
   }
 
   if (this.allowUncaught) {
-    callFn(this.fn);
-    done();
+    if (this.isPending()) {
+      done();
+    } else {
+      callFn(this.fn);
+    }
     return;
   }