Attempt fix for $protectionlevel/type mismatch in $wiki->allpages()

If array() is provided for both $protectionlevels and
$protectiontypes, no error should be thrown.
Tweak to allow $protectionlevels to not be set
Merge pull request #9 from Jarry1250/patch-1

Attempt fix for $protectionlevel/type mismatch in $wiki->allpages()