[backport] Prevent incompatible connections to SubgraphInputNode occupied slots (cherry-pick #4984)#4993

christian-byrne merged 1 commit intocore/1.25Comfy-Org/ComfyUI_frontend:core/1.25from

cherry-pick-4984-to-core-1.25Comfy-Org/ComfyUI_frontend:cherry-pick-4984-to-core-1.25Copy head branch name to clipboard