MINOR: cli: do not call the release handler on internal error.

It's dangerous to call this on internal state error, because it risks
to perform a double-free. This can only happen when a state is not
handled. Note that the switch/case currently doesn't offer any option
for missed states since they're all declared. Better fix this anyway.
The fix was tested by commenting out some entries in the switch/case.
diff --git a/src/dumpstats.c b/src/dumpstats.c
index 87e62eb..bdfb7e3 100644
--- a/src/dumpstats.c
+++ b/src/dumpstats.c
@@ -2554,8 +2554,7 @@
 				break;
 #endif
 			default: /* abnormal state */
-				cli_release_handler(appctx);
-				appctx->st0 = STAT_CLI_PROMPT;
+				si->flags |= SI_FL_ERR;
 				break;
 			}