FIX: ignore SVGs when regenerating missing optimized images.

When running `rake uploads:regenerate_missing_optimized`,
a `Discourse::InvalidAccess` will be raised if an SVG
file is being processed as `OptimizedImage.prepend_decoder!`
doesn't support the svg extension. This commit simply copies
the original SVG file as the thumbnail, just like currently
`OptimizedImage.create_for` does.

lib/tasks/uploads.rake

@@ -353,7 +353,16 @@ def regenerate_missing_optimized
 
         if File.exist?(original) && File.size(original) > 0
           FileUtils.mkdir_p(File.dirname(thumbnail))
-          OptimizedImage.resize(original, thumbnail, optimized_image.width, optimized_image.height)
+          if upload.extension == "svg"
+            FileUtils.cp(original, thumbnail)
+          else
+            OptimizedImage.resize(
+              original,
+              thumbnail,
+              optimized_image.width,
+              optimized_image.height,
+            )
+          end
           putc "#"
         else
           missing_uploads << original