Checking if the input string while parsing the SAM header is not empty

[r78v10a07]

Hi, I've found some odds BAM files with a TAB at the end of the header lines. I added this check condition to avoid a segmentation fault. Thanks, Roberto

[heavywatal]

Good point. But the large diff because of additional indentation can be avoided by using continue like this:

if (tokenIter->empty()) {continue;}