W&B dict copy to fix change bug (#12779)

Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>

ultralytics/utils/callbacks/wb.py

@@ -100,7 +100,7 @@ def _plot_curve(
 
 def _log_plots(plots, step):
     """Logs plots from the input dictionary if they haven't been logged already at the specified step."""
-    for name, params in plots.items():
+    for name, params in plots.copy().items():  # shallow copy to prevent plots dict changing during iteration
         timestamp = params["timestamp"]
         if _processed_plots.get(name) != timestamp:
             wb.run.log({name.stem: wb.Image(str(name))}, step=step)