[BUG] RCA saving fails if there is a NaN value present

[kshitij123456]

Describe the bug

Due to input data having less than 30 rows for a month, when we resample it for the line graph, NaN values can creep up into it. These are then rejected by the database.

Logs

[2021-10-27 12:59:09,636] ERROR in rca_controller: Error in storing output.
Traceback (most recent call last):
  File "/usr/local/lib/python3.8/dist-packages/sqlalchemy/engine/base.py", line 1750, in _execute_context
    self.dialect.do_executemany(
  File "/usr/local/lib/python3.8/dist-packages/sqlalchemy/dialects/postgresql/psycopg2.py", line 903, in do_executemany
    context._psycopg2_fetched_rows = xtras.execute_values(
  File "/usr/local/lib/python3.8/dist-packages/psycopg2/extras.py", line 1292, in execute_values
    cur.execute(b''.join(parts))
psycopg2.errors.InvalidTextRepresentation: invalid input syntax for type json
LINE 1: ...UES (14, '2021-10-26'::date, 'line', 'mom', NULL, '[{"date":...
                                                             ^
DETAIL:  Token "NaN" is invalid.
CONTEXT:  JSON data, line 1: ....0}, {"date": "2021/10/02 00:00:00", "value": NaN...