Werk #18119: Fix tag drop-down with a single choice

Component	Setup
Title	Fix tag drop-down with a single choice
Date	Jun 4, 2025
Level	Trivial Change
Class	Bug Fix
Compatibility	Incompatible - Manual interaction might be required
Checkmk versions & editions	2.5.0b1 Not yet released Checkmk Raw (CRE), Checkmk Enterprise (CEE), Checkmk Cloud (CCE), Checkmk MSP (CME) 2.4.0p5 Checkmk Raw (CRE), Checkmk Enterprise (CEE), Checkmk Cloud (CCE), Checkmk MSP (CME) 2.3.0p35 Not yet released Checkmk Raw (CRE), Checkmk Enterprise (CEE), Checkmk Cloud (CCE), Checkmk MSP (CME)

After the changes made in Werk #17836, some additional legacy code needed to be removed to support tag options when there is only one choice available.

This may have created rules with the null value set, which is not supported anymore. Therefore, running cmk-update-config is needed to run post update. This will remove the null tag from existing rules.

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