Added property getter empty tests
testMethodGetCssEmpty
testMethodGetAdminCssEmpty
testMethodGetScriptsEmpty
testMethodGetAdminScriptsEmpty
testMethodGetMetaboxesEmpty
testMethodGetHelpTabsEmpty
modified testMethodAddHelpTabFail
removed test dependency
changed to test for WP_Error
modified testMethodGetShortcodes
removed dependency
modified testMethodGetShortcodesEmpty
removed dependency