Corrected a bug that throws notices in server log

As not all evens have actually a 'postid', that key needs to be checked inside the IF statement. I just got here from this question http://www.question2answer.org/qa/31356
Re-fixed the IF statement
Minor updates to the plugin metadata

Fixed the update URL.
Increased the version number.
Rephrased the plugin description.
Merge pull request #3 from pupi1985/patch-1

Corrected a bug that throws notices in server log