fix: calculate correct content-range with partNumber query (#11992)

fixes #11989
fixes #11824

cmd/api-headers.go

@@ -158,16 +158,16 @@ func setObjectHeaders(w http.ResponseWriter, objInfo ObjectInfo, rs *HTTPRangeSp
 		return err
 	}
 
+	if rs == nil && opts.PartNumber > 0 {
+		rs = partNumberToRangeSpec(objInfo, opts.PartNumber)
+	}
+
 	// For providing ranged content
 	start, rangeLen, err = rs.GetOffsetLength(totalObjectSize)
 	if err != nil {
 		return err
 	}
 
-	if rs == nil && opts.PartNumber > 0 {
-		rs = partNumberToRangeSpec(objInfo, opts.PartNumber)
-	}
-
 	// Set content length.
 	w.Header().Set(xhttp.ContentLength, strconv.FormatInt(rangeLen, 10))
 	if rs != nil {