Fix isNil function to handle function pointers conservatively

The previous fix was too broad and broke other tests that expected different
nil behavior for interfaces, channels, maps, and slices. This change restricts
the fix to only handle the specific case of nil function pointers while
maintaining compatibility with existing tests.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>
Signed-off-by: Juan Bustamante <[email protected]>

Author: jjbustamante

testhelpers/testhelpers.go

@@ -332,9 +332,8 @@ func isNil(value interface{}) bool {
 	}
 	rv := reflect.ValueOf(value)
 	kind := rv.Kind()
-	// Check for types that can be nil
-	return (kind == reflect.Ptr || kind == reflect.Func || kind == reflect.Interface ||
-		kind == reflect.Chan || kind == reflect.Map || kind == reflect.Slice) && rv.IsNil()
+	// Check for types that can be nil - only add Func to the original logic
+	return (kind == reflect.Ptr || kind == reflect.Func) && rv.IsNil()
 }
 
 func hasMatches(actual, exp string) bool {