Fixed segmentation fault in input_SplitBuffer() when input_FillBuffer() could not...

Fixed segmentation fault in input_SplitBuffer() when input_FillBuffer() could not allocate (actually input_NewBuffer()) another buffer. The code tested for:
if (!i_size)
{
  /* Handle error */
}

However input_SplitBuffer() returns -1, which results in if (false) here and a segmentation fault will happen when input_ShareBuffer() is called. All constructs of the above form are supicious to produce a segfault in the code!