[YCQL] JSONB dereferencing operators return ERROR when applying to NULL input

[nocaway]

In the following example, SELECT statement should have been valid, and the output for jsonb access operator should have been NULL. However, YugaByte returns error.

ycqlsh:test> CREATE TABLE tab( h INT, r INT, v INT, j JSONB, PRIMARY KEY (h, r))   with transactions = {'enabled' : true};
ycqlsh:test> INSERT INTO tab(h, r, v) VALUES (7, 14, 21);
ycqlsh:test> select j->>'a' from tab;
ServerError: Server Error. Not enough data to process
select j->>'a' from tab;
^^^^^^
 (ql error -2)

[nocaway]

Fixed in master and backported to 2.1, 2.2, and 2.4.