buffer: dereference before null check fix

This will fix null dereference issue reported by KW

Signed-off-by: Adrian Bonislawski <adrian.bonislawski@intel.com>

Author: abonislawski

src/audio/buffer.c

@@ -159,11 +159,11 @@ void buffer_free(struct comp_buffer *buffer)
 		.buffer = buffer,
 	};
 
-	buf_dbg(buffer, "buffer_free()");
-
 	if (!buffer)
 		return;
 
+	buf_dbg(buffer, "buffer_free()");
+
 	notifier_event(buffer, NOTIFIER_ID_BUFFER_FREE,
 		       NOTIFIER_TARGET_CORE_LOCAL, &cb_data, sizeof(cb_data));