Fix generate thumbnails

Author: hlohaus

g4f/image/__init__.py

@@ -222,13 +222,13 @@ def process_image(image: Image.Image, new_width: int = 800, new_height: int = 40
     # Remove transparency
     if image.mode == "RGBA":
         image.load()
-        white = Image.open('RGB', image.size, (255, 255, 255))
+        white = Image.new('RGB', image.size, (255, 255, 255))
         white.paste(image, mask=image.split()[-1])
-        return white
+        image = white
     # Convert to RGB for jpg format
     elif image.mode != "RGB":
         image = image.convert("RGB")
-    elif save is not None:
+    if save is not None:
         image.save(save, exif=b"")
     return image