Use Image Style Root fails if image style includes file conversion

[yorkshire-pudding]

Steps to reproduce

1. Install "Stage File Proxy" and also the "Image Effects" module and enable the "Image Effects Color and Conversion Actions" submodule
2. Create an image style that includes file conversion
3. Add some images on nodes using this style.
4. On the local or other site using "Stage File Proxy" and set Use Image Style Root to true.
5. Load the page

Expected result
Image loads

Actual result
Image does not load and if enabled produces warnings.