Dear Bach Pham,
i set the Variable $title_article with my Custom Text and ist works Fine.. i add a line between 136 - 137
Perhaps, you can add an option "Custom Message" and set the variable with the custom text when the field is not empty..
And an language option to set the social network scripts to German like "de-DE" was fine
Best Regards
René
PS: do you know whether is possible to Open the Share Windows from Facebook and google Plus in a New window Not in a iframe? My Modal window is small and the iframes Breaks the format of my modal