Allow 0 in string form in addJavascriptVar

Signed-off-by: Yoshi2889 <rick.2889@gmail.com>
! Hitting enter from a text field in the profile shouldn't trigger the signature preview button...

Signed-off-by: Michael Eshom <oldiesmann@oldiesmann.us>
Merge pull request #2167 from Oldiesmann/release-2.1

! Hitting enter from a text field in the profile shouldn't trigger the s...
! Trying to preview a warning message didn't work (fixes #2147)
Merge pull request #2168 from Oldiesmann/release-2.1

! Trying to preview a warning message didn't work (fixes #2147)
Merge pull request #2163 from Yoshi2889/js-var-fix

Allow 0 in string form in addJavascriptVar