Handle null FileRootSize values on Postgres

[labkey-jeckels]

Rationale

I'm seeing this exception Postgres 14. I have a few containers with invalid file roots so the size is null.

Caused by: org.postgresql.util.PSQLException: ERROR: column "filerootsize" is of type bigint but expression is of type character varying
  Hint: You will need to rewrite or cast the expression.
  Position: 69
	at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2733)
...
	at org.labkey.api.data.SqlExecutor.execute(SqlExecutor.java:75)
	at org.labkey.filecontent.FileRootMaintenanceTask.lambda$run$0(FileRootMaintenanceTask.java:86)

Changes

• Specify the type of the null