even better "parent" button selector

fixes regression from dee61fc28ba6d3e6c82c41dbd5c719ade5c0ac8a. probably slightly more efficient, too.

assumes that "permalink" button will always be first button, which is a terrible assumption but it's still better than the previous version
showParent.show checks for parent comment existence before setting up hover div

Look before you leap, because I disapprove of try-catch in JavaScript; and it's slightly more efficient this way
even better "parent" button selector

fixes regression from dee61fc28ba6d3e6c82c41dbd5c719ade5c0ac8a. probably slightly more efficient, too.

assumes that "permalink" button will always be first button, which is a terrible assumption but it's still better than the previous version
showParent.show checks for parent comment existence before setting up hover div

Look before you leap, because I disapprove of try-catch in JavaScript; and it's slightly more efficient this way
Merge branch 'showparent-fix2' of github.com:andytuba/Reddit-Enhancement-Suite into showparent-fix2
Merge pull request #283 from andytuba/showparent-fix2

Fix parent hover again