FIX - don't attempt to optimized animated images (#11031)

* FIX - don't attempt to optimized animated images

* ensure_safe_paths before calling ImageMagick

lib/upload_creator.rb

@@ -126,7 +126,7 @@ class UploadCreator
       if is_image
         @upload.thumbnail_width, @upload.thumbnail_height = ImageSizer.resize(*@image_info.size)
         @upload.width, @upload.height = @image_info.size
-        @upload.animated = FastImage.animated?(@file)
+        @upload.animated = animated?(@file)
       end
 
       add_metadata!
@@ -177,6 +177,25 @@ class UploadCreator
     end
   end
 
+  def animated?(file)
+    OptimizedImage.ensure_safe_paths!(file.path)
+
+    # TODO - find out why:
+    #   FastImage.animated?(@file)
+    # doesn't seem to identify all animated gifs
+    @frame_count ||= begin
+      command = [
+        "identify",
+        "-format", "%n\\n",
+        file.path
+      ]
+
+      frames = Discourse::Utils.execute_command(*command).to_i rescue 1
+    end
+
+    @frame_count > 1
+  end
+
   MIN_PIXELS_TO_CONVERT_TO_JPEG ||= 1280 * 720
 
   def convert_png_to_jpeg?
@@ -267,6 +286,8 @@ class UploadCreator
   end
 
   def should_alter_quality?
+    return false if animated?(@file)
+
     @upload.target_image_quality(@file.path, SiteSetting.recompress_original_jpg_quality).present?
   end