Ensure matplotlib backend gets reset with plt_settings (#15759)

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

ultralytics/utils/__init__.py

@@ -219,16 +219,19 @@ def plt_settings(rcparams=None, backend="Agg"):
         def wrapper(*args, **kwargs):
             """Sets rc parameters and backend, calls the original function, and restores the settings."""
             original_backend = plt.get_backend()
-            if backend.lower() != original_backend.lower():
+            switch = backend.lower() != original_backend.lower()
+            if switch:
                 plt.close("all")  # auto-close()ing of figures upon backend switching is deprecated since 3.8
                 plt.switch_backend(backend)
 
-            with plt.rc_context(rcparams):
-                result = func(*args, **kwargs)
-
-            if backend != original_backend:
-                plt.close("all")
-                plt.switch_backend(original_backend)
+            # Plot with backend and always revert to original backend
+            try:
+                with plt.rc_context(rcparams):
+                    result = func(*args, **kwargs)
+            finally:
+                if switch:
+                    plt.close("all")
+                    plt.switch_backend(original_backend)
             return result
 
         return wrapper