FIX: We should be able to import value '0'

htdocs/core/modules/import/import_csv.modules.php

@@ -401,7 +401,7 @@ class ImportCsv extends ModeleImports
 						// Make some tests on $newval
 
 						// Is it a required field ?
-						if (preg_match('/\*/',$objimport->array_import_fields[0][$val]) && ($newval==''))
+						if (preg_match('/\*/',$objimport->array_import_fields[0][$val]) && ((string) $newval==''))
 						{
 							$this->errors[$error]['lib']=$langs->trans('ErrorMissingMandatoryValue',$key);
 							$this->errors[$error]['type']='NOTNULL';

htdocs/core/modules/import/import_xlsx.modules.php

@@ -419,7 +419,7 @@ class Importxlsx extends ModeleImports
 						// Make some tests on $newval
 
 						// Is it a required field ?
-						if (preg_match('/\*/',$objimport->array_import_fields[0][$val]) && ($newval==''))
+						if (preg_match('/\*/',$objimport->array_import_fields[0][$val]) && ((string) $newval == ''))
 						{
 							$this->errors[$error]['lib']=$langs->trans('ErrorMissingMandatoryValue',$key);
 							$this->errors[$error]['type']='NOTNULL';