live: ensure image file exists after partclone

check that there is a file and that is accessible

src/live/ogOperations.py

@@ -478,6 +478,10 @@ class OgLiveOperations:
 
             ogExtendFs(disk, partition)
 
+            if os.access(f'{image_path}', os.R_OK) == False:
+                    logging.error(f'Cannot access partclone image file {image_path}')
+                    raise ValueError('Cannot access image file')
+
             image_info = ogGetImageInfo(image_path)
         except:
             self._restartBrowser(self._url)