Description of problem:
In a C/C++ backtrace, if the crash thread has only four frames and the bottom one is the dummy frame under "clone", the backtrace will get a low rating and abrt will consider it unusable, even though all the information one could want is there.  Here is an example (I manually hacked abrt to allow me to report it as bug 592521):

Thread 1 (Thread 21446):
#0  0x00007f4dcf70c5e9 in jack_watchdog_thread (arg=0x22fe010) at engine.c:954
        engine = 0x22fe010
        timo = {tv_sec = 10, tv_nsec = 0}
#1  0x00007f4dcf062a3a in start_thread (arg=0x7f4dcf9e5710)
    at pthread_create.c:297
        __res = <value optimized out>
        pd = 0x7f4dcf9e5710
        now = <value optimized out>
        unwind_buf = {cancel_jmp_buf = {{jmp_buf = {139972172470032, 
                -3132889451195097733, 140736863387184, 0, 0, 3, 
                3034901235276881275, 3034902406592896379}, 
              mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0x0, 0x0}, 
            data = {prev = 0x0, cleanup = 0x0, canceltype = 0}}}
        not_first_call = <value optimized out>
        sp = <value optimized out>
        freesize = <value optimized out>
#2  0x00007f4dcebbd62d in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
No locals.
#3  0x0000000000000000 in ?? ()

The rating algorithm should be changed to avoid this outcome.  It may work to simply ignore frames with an address of zero.

Version-Release number of selected component (if applicable):
abrt-1.0.9-2.fc12.x86_64

How reproducible:
Always

Steps to Reproduce:
1. Follow the steps in bug 592521 to trigger abrt.
2. Press "Report".

Actual results:
abrt says the backtrace is unusable and does not allow it to be reported.  It recommends installing the debuginfo, which does not help.

Expected results:
abrt allows reporting the backtrace.