Kibana version: 6.5.4

Elasticsearch version: 6.5.4

Server OS version: CentOS Linux release 7.6.1810 (kernel 3.10.0-957.1.3.el7.x86_64)

Browser version: Google Chrome Version 71.0.3578.98 (Official Build) (64-bit)

Browser OS version: Google Chrome Version 71.0.3578.98 (Official Build) (64-bit)

Original install method (e.g. download page, yum, from source, etc.): yum (rpm installation)

Describe the bug: Kibana "Clusters / <<cluster_name>> / Elasticsearch / Indices / <<index_name>>" graph "Disk (MB)" "Store (Primaries)" toggle'ing does not work.

Steps to reproduce:

1. Navigate to "localhost:5601/app/monitoring#/elasticsearch/indices/<<index_name>>"
2. Toggle on "Store (Primaries) X MB" from graph Disk (MB)
3. You will see that this "Store" line does not get hidden from the graph, so nothing happens basically (nothing in logfile also)

Expected behavior: If toggle'ing this "Store (Primaries)" ON, there should be only blue line left on that graph.

Screenshots (if relevant):

Errors in browser console (if relevant):

Provide logs and/or server output (if relevant): No errors in browser console.

Any additional context: