test: ignore MemProfileRecords with no live objects in finprofiled.go

This test erroneously assumes that there will always be at least one
live object accounted for in a MemProfileRecord. This is not true; all
memory allocated from a particular location could be dead.

Fixes #64153.

Change-Id: Iadb783ea9b247823439ddc74b62a4c8b2ce8e33e
Reviewed-on: https://go-review.googlesource.com/c/go/+/542736
Reviewed-by: Cherry Mui <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: mknyszek

test/finprofiled.go

@@ -57,6 +57,11 @@ func main() {
 	for _, p := range prof {
 		bytes := p.AllocBytes - p.FreeBytes
 		nobj := p.AllocObjects - p.FreeObjects
+		if nobj == 0 {
+			// There may be a record that has had all of its objects
+			// freed. That's fine. Avoid a divide-by-zero and skip.
+			continue
+		}
 		size := bytes / nobj
 		if size == tinyBlockSize {
 			totalBytes += bytes