Argument "" isn't numeric in numeric lt

[ToterEngel]

Since version 2.5.2:

[OK] InnoDB buffer pool / data size: 4.0G / 206.1M
Argument "" isn't numeric in numeric lt (<) at ./mysqltuner.pl line 6375 (#1)
(W numeric) The indicated string was fed as an argument to an operator
that expected a numeric value instead. If you're fortunate the message
will identify which operator was so unfortunate.

Note that for the Inf and NaN (infinity and not-a-number) the
definition of "numeric" is somewhat unusual: the strings themselves
(like "Inf") are considered numeric, and anything following them is
considered non-numeric.

[jmrenouard]

Hi @ToterEngel
Duplicated with #759