./src/espeak-ng -v ar --path=$PWD 5777
would access out of the vowel_stress array, because GetVowelStress, in the
phcode == phonSYLLABIC case, only increments count if stress is 0. This
code seems fishy, and is not coherent with the loop in SetWordStress. I
made it similar to the other case above, thus fixing the out-of-bound
access.
This is modifiying the stress in the tn test, I don't know whether this
is expected.