Traceback when submitting duplicate when Duplicate Variation is not set

[xispa]

Steps to reproduce

1. Create an Analysis Request with an Analysis Services with no value for Duplicate Variation field
2. Create a worksheet and assign the analysis from the previously created AR
3. Add a Duplicate of the previous analysis
4. Type the results and submit

Current behavior

Traceback (innermost last):
  Module ZPublisher.Publish, line 138, in publish
  Module ZPublisher.mapply, line 77, in mapply
  Module ZPublisher.Publish, line 48, in call_object
  Module bika.lims.browser.worksheet.views.results, line 65, in __call__
  Module Products.Five.browser.pagetemplatefile, line 125, in __call__
  Module Products.Five.browser.pagetemplatefile, line 59, in __call__
  Module zope.pagetemplate.pagetemplate, line 132, in pt_render
  Module five.pt.engine, line 98, in __call__
  Module z3c.pt.pagetemplate, line 158, in render
  Module chameleon.zpt.template, line 297, in render
  Module chameleon.template, line 191, in render
  Module chameleon.template, line 171, in render
  Module 7b128d75da87caa8d29493a9d09a0f38.py, line 1352, in render
  Module bff4424a594e64e8de9abb79b1fda941.py, line 1449, in render_master
  Module bff4424a594e64e8de9abb79b1fda941.py, line 604, in render_content
  Module 7b128d75da87caa8d29493a9d09a0f38.py, line 1256, in __fill_content_core
  Module five.pt.expressions, line 161, in __call__
  Module bika.lims.browser.bika_listing, line 1569, in contents_table
  Module bika.lims.browser.bika_listing, line 1747, in __init__
  Module bika.lims.browser.worksheet.views.analyses, line 155, in folderitems
  Module bika.lims.browser.analyses, line 516, in folderitems
  Module bika.lims.browser.bika_listing, line 1008, in folderitems
  Module bika.lims.browser.worksheet.views.analyses, line 106, in folderitem
  Module bika.lims.browser.analyses, line 473, in folderitem
  Module bika.lims.browser.analyses, line 679, in _folder_item_result
  Module bika.lims.content.abstractanalysis, line 902, in getFormattedResult
  Module bika.lims.content.duplicateanalysis, line 159, in getResultsRange
  Module bika.lims.api, line 1235, in to_float
  Module bika.lims.api, line 215, in fail
BikaLIMSError: Value None is not floatable

 - Expression: "provider:plone.abovecontentbody"
 - Filename:   ... rc/senaite/lims/skins/senaite_templates/main_template.pt
 - Location:   (line 146: col 90)
 - Source:     ... ent="structure provider:plone.abovecontentbody" tal:conditio ...
                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 - Expression: "provider:plone.abovecontent"
 - Filename:   ... rc/senaite/lims/skins/senaite_templates/main_template.pt
 - Location:   (line 88: col 67)
 - Source:     ... ntent="structure provider:plone.abovecontent" tal:condition= ...
                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 - Expression: "here/main_template/macros/master"
 - Filename:   ... ika/lims/browser/worksheet/views/../templates/results.pt
 - Location:   (line 5: col 23)
 - Source:     metal:use-macro="here/main_template/macros/master"
                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 - Arguments:  repeat: {...} (0)
               template: <ViewPageTemplateFile - at 0x7f1a392ed450>
               views: <ViewMapper - at 0x7f1a32fbbe50>
               modules: <instance - at 0x7f1a57cef0e0>
               args: <tuple - at 0x7f1a5f709050>
               here: <ImplicitAcquisitionWrapper WS18-008 at 0x7f1a3e89e690>
               user: <ImplicitAcquisitionWrapper - at 0x7f1a33328640>
               nothing: <NoneType - at 0x8f5320>
               translate: <function translate at 0x7f1a331b4848>
               container: <ImplicitAcquisitionWrapper WS18-008 at 0x7f1a3e89e690>
               root: <ImplicitAcquisitionWrapper Zope at 0x7f1a332f2960>
               request: <instance - at 0x7f1a3b6d5e18>
               wrapped_repeat: <SafeMapping - at 0x7f1a32fe6c00>
               traverse_subpath: <list - at 0x7f1a39cd6368>
               default: <object - at 0x7f1a5f626560>
               loop: {...} (2)
               context: <ImplicitAcquisitionWrapper WS18-008 at 0x7f1a3e89e690>
               view: <ManageResultsView manage_results at 0x7f1a3338a6d0>
               target_language: <NoneType - at 0x8f5320>
               macroname: master
               options: {...} (0)

Expected behavior

The results are stored without Traceback