"show fabric monitor capacity" index error for threshold

[jfeng-arista]

Description

"show fabric monitor capacity" shows index error for threshold when the feature get disabled.

Steps to reproduce the issue

1. disable the fabric link moniotring feature
2. issue "show fabric monitor capacity" command

Describe the results you received

Describe the results you expected

Additional information you deem important (e.g. issue happens only occasionally)

Output of show version

(paste your output here)