suffix may be used before being assigned in qmin/ans3/ans.py

Coverity reports Bad use of null-like value

139    if lqname == "zoop.boing." and rrtype == NS:
     	CID 350722 (#1 of 7): Bad use of null-like value (FORWARD_NULL) [select issue]
140        r.answer.append(
141            dns.rrset.from_text(lqname + suffix, 1, IN, NS, "ns3." + suffix)
142        )
143        r.flags |= dns.flags.AA
   	11. Condition endswith(lqname, "icky.ptang.zoop.boing."), taking true branch.
144    elif endswith(lqname, "icky.ptang.zoop.boing."):
   	
CID 350722 (#5 of 7): Bad use of null-like value (FORWARD_NULL)
12. invalid_operation: Invalid operation on null-like value suffix.
145        r.authority.append(
146            dns.rrset.from_text(
147                "icky.ptang.zoop.boing." + suffix,
148                1,
149                IN,
150                NS,
151                "a.bit.longer.ns.name." + suffix,
152            )
153        )
154    elif endswith("icky.ptang.zoop.boing.", lqname):
     	CID 350722 (#3 of 7): Bad use of null-like value (FORWARD_NULL) [select issue]
155        r.authority.append(
156            dns.rrset.from_text(
157                "zoop.boing." + suffix,
158                1,
159                IN,
160                SOA,
161                "ns3." + suffix + " hostmaster.arpa. 2018050100 1 1 1 1",
162            )
163        )
164        if bad:
165            r.set_rcode(NXDOMAIN)
166        if ugly:
167            r.set_rcode(FORMERR)
168    elif endswith(lqname, "zoop.boing."):
     	CID 350722 (#4 of 7): Bad use of null-like value (FORWARD_NULL) [select issue]
169        r.authority.append(