Query Which is not supposted to list NULLS is listing NULLS also

CREATE TABLE tbljobincharge (

jassignedid int4 DEFAULT nextval('"tbljobincharge_jassignedid_seq"'::text) NOT NULL,

projectid int4 NOT NULL,

accountid int4 NOT NULL,

completeddate timestamp,

jobcompleted bool DEFAULT 'f' NOT NULL,

jobcomments text,

satisid int4,

priorityid int4 DEFAULT 0 NOT NULL,

active bool DEFAULT 't' NOT NULL,

remarks text,

noofunits int4 DEFAULT 0 NOT NULL,

jobassigneddate timestamp,

assignedby int4 )

But Query

SELECT jassignedid, JobComments FROM tblJobIncharge WHERE JobComments IS NOT NULL AND projectid >= 50 AND projectid <= 100

Which is not supposed to list NULLS  is listing NULLS also. Is there any alternative to write a query to list 'not null' result. I am attaching result set of query for you reference.

Thanks And Regards

Sreedhar