Error Running Blast2Sam.Pl

I am trting to convert blastn (from blast-2.2.25+) output to sam format using samtools "blast2sam.pl" script.

Any suggestions to rectify the error?

Error message:

Use of uninitialized value in subtraction (-) at ./blast2sam.pl line 58, <> line 422362.
Use of uninitialized value in subtraction (-) at ./blast2sam.pl line 58, <> line 422362.
@HWI-ST388-W7D:1:1101:1221:187650#0/1   0       gb|DQ079892.1|  0       255     0M      *       0       0       *       *       AS:i:147        EV:Z:5e-34

Line 422362 (pasted below) is the last line in the blastoutput file

Gap Penalties: Existence: 0, Extension: 2.5