if (aux) { // check if aux is present
bam_header_t *textheader = fp->header;
fp->header = sam_header_read2((const char*)aux);
+ if (fp->header == 0) goto open_err_ret;
append_header_text(fp->header, textheader->text, textheader->l_text);
bam_header_destroy(textheader);
}