After-merge fix: Correct an assertion

During IMPORT TABLESPACE, we do invoke
buf_flush_init_for_writing() with block==NULL and newest_lsn!=0.

storage/innobase/buf/buf0flu.cc

@@ -854,7 +854,7 @@ buf_flush_init_for_writing(
 	ut_ad(block == NULL || block->frame == page);
 	ut_ad(block == NULL || page_zip_ == NULL
 	      || &block->page.zip == page_zip_);
-	ut_ad(!srv_safe_truncate || !block == !newest_lsn);
+	ut_ad(!srv_safe_truncate || !block || newest_lsn);
 	ut_ad(page);
 	ut_ad(!srv_safe_truncate || !newest_lsn || fil_page_get_type(page));