slapos_jio: Ignore if value isn't provided

  It is safe to ignore if value is none (it indicates the user sent a raw data).

master/bt5/slapos_jio/SkinTemplateItem/portal_skins/slapos_hal_json_style/InstanceTree_edit.py

@@ -21,8 +21,9 @@ def isSoftwareTypeChanged(software_type):
   current_software_type = context.getSourceReference()
   if software_type in base_type and current_software_type in base_type:
     return False
-  else:
-    return current_software_type != software_type
+  if software_type in [None, ""]:
+    return False
+  return current_software_type != software_type
 
 if 'software_type' in request and isSoftwareTypeChanged(request['software_type']):
   raise ValueError("Change Software Type is forbidden.")