Steps to reproduce:

1. Create two hosts: Host1=1.1.1.1 and Host2=9.9.9.9 (using the Agent interface; the actual addresses are irrelevant, just something that respond to ping)
2. On Host1 create Zabbix internal item "Ping" with key "icmpping", interval 10s, tag "component: test1"
3. On Host2 create Zabbix internal item "Ping" with key "icmpping", interval 10s, tag "component: test2"
4. On Host1 create graph "Ping", add the item Ping
5. On Host2 create graph "Ping", add the item Ping
6. Wait for data to gather
7. Go to Monitoring - Hosts
8. Click on Graphs for Host1
9. Under Subfilter click on the tag value "test1"
10. Go to Monitoring - Hosts
11. Click on Graphs for Host2

Result:
The Graphs page has Host2 selected but it shows "No data found" under the Subfilter selection. No subfilters are selected in the page.

Expected:
Since there are no Subfilters selected it is expected to show unfiltered (all) graphs for the host.

Commentary:
Apparently the page remembers the previously selected (but visually not indicated) subfilter "test1" but there are no matching graphs for the current host.

Workaround:
Whenever "No data found" is encountered in the Graphs page, click on any tag/value in Subfilter to select it and then click it again to unselect it.