This function attempts to return the first available restart with the string "muffle" in its name. If the condition is an error, it will attempt to find the first restart named "return_error" (used internally in catchr to return a NULL value). If the condition is an "interrupt", it will attempt to find the first restart named "resume". If no such restarts can be found, it returns NULL.
first_muffle_restart(cond)A condition
A restart or NULL if none can be found.