Dereference null return value

If the function actually returns a null value, a null pointer dereference will occur. Return value of function which returns null is dereferenced without checking
/data/mci/3b34054db808e84e865ea3adc167bb30/bazel_cache/8efb34a963653a257fe76e59a8ff65e9/execroot/_main/src/mongo/db/repl/dbcheck/dbcheck.cpp:507: NULL_RETURNS 158662 Assigning: "indexDescriptor" = "nullptr" return value from "findIndexByName".