Null ptr at B062F15-16 coefficient output for a particular request

[mickvf]

There is a null dereference in the RespUtil class at the point of Polynomial section output. This is where it's attempting to produce the B062F15-16 coefficient lines.

Repro:
Make the following request:
http://service.iris.edu/irisws/resp/1/query?net=AV&sta=N20K&loc=EP&cha=LDO&starttime=2020-04-26T00:00:00&endtime=2599-12-31T23:59:59

Expected:
Something like what the station service does...

B062F14     Number of Coefficients:                2
#              Polynomial coefficients:
#              i, coefficient,  error
B062F15-16     null+8.00000E+04  +0.00000E+00
B062F15-16     null+1.50000E-02  +0.00000E+00