slapos_panel: handle software product with only one software type

master/bt5/slapos_panel/SkinTemplateItem/portal_skins/slapos_panel/Project_addSlapOSSoftwareProduct.py

@@ -11,6 +11,9 @@ software_product.newContent(
   title=software_release,
   url_string=software_release
 )
+
+if same_type(software_type_list, ""):
+  software_type_list = [software_type_list]
 for software_type in software_type_list:
   software_product.newContent(
     portal_type="Software Product Type Variation",