[BUGFIX] number_format() expects parameter 1 to be double

In stdWrap function numberFormat $content is a string.
Make sure this is a float value when it is passed into
PHP function number_format.

Change-Id: If4a98ae8238264f94f771c997fbe6cac98311912
Resolves: #50868
Releases: 6.2, 6.1, 6.0, 4.7, 4.5
Reviewed-on: https://review.typo3.org/22936
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring