tkt-72097: fix traceback in pool.py (#2477)

fix traceback in pool.py

Ticket: #72097

src/middlewared/middlewared/plugins/pool.py

@@ -405,7 +405,7 @@ def _topology(self, x, geom_scan=True):
                 if path.startswith('/dev/'):
                     device = self.middleware.call_sync('disk.label_to_dev', path[5:], geom_scan)
                 x['device'] = device
-                x['disk'] = RE_DISKPART.sub(r'\1', device)
+                x['disk'] = RE_DISKPART.sub(r'\1', device) if device else None
             for key in x:
                 if key == 'type' and isinstance(x[key], str):
                     x[key] = x[key].upper()