garray: Update NULL termination after copying array content
ptr_array_new(len, ., TRUE) ensures that there are at least len+1 elements in pdata, and that pdata[0] is null, but leaves the rest of pdata uninitialized. After copying the array data into pdata[1] to pdata[len-1] inclusive, we still need to make sure pdata[len] is a null terminator.
Resolves: #2877 (closed)