diff --git a/desktop_env/evaluators/metrics/slides.py b/desktop_env/evaluators/metrics/slides.py
index dac4fd1..90eea64 100644
--- a/desktop_env/evaluators/metrics/slides.py
+++ b/desktop_env/evaluators/metrics/slides.py
@@ -49,11 +49,16 @@ def check_image_stretch_and_center(modified_ppt, original_ppt):
 
     the_image = original_slide_images[0]
 
+    the_modified_image = None
+
     # Get the images that modified in width and height
     for modified_image in modified_slide_images:
         if the_image.image.blob == modified_image.image.blob:
             the_modified_image = modified_image
 
+    if the_modified_image is None:
+        return 0.
+
     if (abs(the_modified_image.width - original_pres.slide_width) > Inches(0.5) or
             abs(the_modified_image.height - original_pres.slide_height) > Inches(0.5) or
             abs(the_modified_image.left - (original_pres.slide_width - the_modified_image.width) / 2) > Inches(0.5) or