MDEV-14508: encryption.innodb-compressed-blob failed in buildbot, assertion in btr0cur.cc line 1398

Before that line there is call to buf_page_get_gen that could
return block = NULL when decrypting a page fails. However,
we should set error to be != DB_SUCCESS also. In error log
there was error about decompression but in that code there
is one case where error is not set correctly.

storage/innobase/buf/buf0buf.cc

@@ -3453,6 +3453,8 @@ buf_page_get_gen(
 				buf_block_unfix(fix_block);
 				buf_pool_mutex_exit(buf_pool);
 				rw_lock_x_unlock(&fix_block->lock);
+
+				*err = DB_PAGE_CORRUPTED;
 				return NULL;
 			}
 		}

storage/xtradb/buf/buf0buf.cc

@@ -3369,6 +3369,8 @@ buf_page_get_gen(
 				mutex_enter(&buf_pool->LRU_list_mutex);
 				buf_block_unfix(fix_block);
 				mutex_exit(&buf_pool->LRU_list_mutex);
+
+				*err = DB_PAGE_CORRUPTED;
 				return NULL;
 			}
 		}