add translation

locale/es.po

@@ -54,6 +54,10 @@ msgctxt "model:ir.sequence.type,name:sequence_type_edocument"
 msgid "Electronic Document"
 msgstr "Documentación Electrónica"
 
-msgctxt "model:product.template,EDI_code:"
+msgctxt "field:product.template,EDI_code:"
+msgid "EDI Code"
+msgstr "Código EDI"
+
+msgctxt "field:party.address,EDI_code:"
 msgid "EDI Code"
 msgstr "Código EDI"

stock.py

@@ -20,7 +20,7 @@ class UnitLoad:
     __name__ = 'stock.unit_load'
 
     def get_best_before(self):
-        return None
+        return ''
 
     def get_sscc(self):
         if self.shipment_out:
@@ -30,7 +30,7 @@ class UnitLoad:
             edi_code = edi_codes[0][:6] if edi_codes else '000000'
             code = '00' + edi_code + self.code[-9:].zfill(len(self.code[-9:])-9)
             return code + str(self._sscc_control_digit(code))
-        return None
+        return ''
 
     def get_grai(self):
         return None