Fixed Upload button on High Level Source Editing popup.

STUD-1773

Upload button on High Level Source Editing pop up is not working properly. Not uploading and the Upload pop up closes when you click cancel 4 to 5 times.

Every time when user clicks on the "Launch Latex Source Compiler" link then and input element of type file is appended to the div, for example if user clicked 3 times on the link then it appends 3 input element of type file added in the div and after that when user clicked on upload button it will trigger 3 times choose file window.