fix: negative start bigger than the file size

Author: lidel

gateway/serve_http_content.go

@@ -482,7 +482,10 @@ func seekToRangeStart(data io.Seeker, ra *ByteRange, size int64) error {
 			if ra.To != nil {
 				return fmt.Errorf("invalid range: negative start without a nil end")
 			}
-			start = size + ra.From
+			start = size + ra.From - 1
+			if start < 0 {
+				return fmt.Errorf("invalid range: negative start bigger than the file size")
+			}
 		} else {
 			start = ra.From
 		}