When aborting the event source using abort controller, no callbacks (onError / onClose) are fired

When aborting the request using abortController, fetch will throw a error with AbortError as name to identify whether it is aborted by the user or not. But when abort is used on fetchEventSource, neither onClose or onError are fired. onError should be throwing a error when this happens. Due to this, we have to wire up logics differently due to this shortcoming..