buffer: Don't Serialize in case the buffer is shared

Otherwise we unnecessarily serialize the shared buffer every time when closing
a bufpane with this buffer, so every such serialize overwrites the previous one,
thus only the last serialize (when closing the last instance of the buffer, i.e.
when actually closing the file, i.e. when the buffer is not shared anymore) will
be used anyway.

Author: JoeKar

internal/buffer/buffer.go

@@ -531,10 +531,10 @@ func (b *Buffer) Close() {
 // Fini should be called when a buffer is closed and performs
 // some cleanup
 func (b *Buffer) Fini() {
-	if !b.Modified() {
-		b.Serialize()
-	}
 	if !b.Shared() {
+		if !b.Modified() {
+			b.Serialize()
+		}
 		b.CancelBackup()
 	}