[t:5103] Fix tests that don't provide a txn for logging commits/aborts/prepares

git-svn-id: file:///svn/toku/tokudb@44745 c7de825b-a66e-492c-adef-691d508d4ae1

ft/logformat.c

@@ -408,7 +408,7 @@ generate_log_writer (void) {
                             break;
                         }
                         case ASSERT_BEGIN_WAS_LOGGED: {
-                            fprintf(cf, "  invariant(txn->begin_was_logged);\n");
+                            fprintf(cf, "  invariant(!txn || txn->begin_was_logged);\n");
                             break;
                         }
                         case IGNORE_LOG_BEGIN: break;