fixed warning "There are some data after the end of the payload data" with multi volume archives

SevenZip/StreamWrappers.cs

@@ -415,7 +415,7 @@ public int Write(byte[] data, uint size, IntPtr processedSize)
             int offset = 0;
             var originalSize = (int) size;
             Position += size;
-            _overallLength = Math.Max(Position + 1, _overallLength);
+            _overallLength = Math.Max(Position, _overallLength);
             while (size > _volumeSize - Streams[CurrentStream].Position)
             {
                 var count = (int) (_volumeSize - Streams[CurrentStream].Position);
@@ -493,4 +493,4 @@ private void OnBytesWritten(IntEventArgs e)
         }
     }
 #endif
-}
+}