[#2207] Removed unnecessary null check

bug: anti-dce
model: |
  %tobool130 = icmp ne %"class.irods::auth"* %86, null, !dbg !1643
  -->  true
  ************************************************************
  if.then131:
  call void (i32, i8*, ...)* @rodsLog(i32 3, i8* getelementptr inbounds ([39 x i8]* @.str61, i32 0, i32 0)), !dbg !1645
  br label %if.end132, !dbg !1647
stack:
  - /home/kellerb/software/root-stack/irods/plugins/auth/osauth/libosauth.cpp:727:0
ncore: 1
core:
  - /home/kellerb/software/root-stack/irods/plugins/auth/osauth/libosauth.cpp:723:0
    - null pointer dereference