389 DS segfaults on libsyntax-plugin.so - part 1
    
    https://bugzilla.redhat.com/show_bug.cgi?id=516611
    Resolves: bug 516611
    Bug Description: 389 DS segfaults on libsyntax-plugin.so - part 1
    Reviewed by: nkinder (Thanks!)
    Branch: Directory_Server_8_2_Branch
    Fix Description: Check for NULL bvals in the string syntax filter functions
    ava, sub, and key generation
    Platforms tested: RHEL5 x86_64
    Flag Day: no
    Doc impact: no
    (cherry picked from commit ea0cdc6ce1cf1c9a690acab443e6df11b3e0fe15)