request #7535 TV3 to TV5 : a float field with no value generate errors in XML import

Deal with NULL values for float and int fields

Change-Id: Iddd5a6f2327607f1e6f721136e9656e0ee970016
Merge commit 'refs/changes/43/3143/2' of ssh://gerrit.tuleap.net:29418/tuleap into HEAD

* ssh://gerrit.tuleap.net:29418/tuleap:
  request #7535 TV3 to TV5 : a float field with no value generate errors in XML import

Change-Id: Ia724c7bf7ab4654ae1c0b398c75ef5778c3b294a
This is Tuleap 7.6.99.17

Change-Id: I1f10f9115c9e4b9901a6a02801f1425f8191473e