f069f5be7f
Previously, with the render display mode set to "Image Editor", we'd use any image editor that doesn't already show a (non-render-result) image, even if they weren't set to view mode (but UV, paint or mask mode). It could be confusing or annoying when using an Image Editor for a purpose that the mode wasn't created for. Note that with the introduction of a UV sub-Editor, the old behavor was even more confusing. Changing a UV Editor to show the render result was weird.