Suspected bug: /v1/actions/execute-command may accidentally update existing check result

This is something that caught my attention while looking over something else. I haven't tested if the bug I suspect actually exists, I just wanted to write this down here so it isn't forgotten. Feel free to confirm or disprove it.

The handler for /v1/actions/execute-command takes the last check result of a checkable: https://github.com/Icinga/icinga2/blob/eddd4c7bf7554a3700abe880781a7646703b7e5f/lib/icinga/apiactions.cpp#L758

And passes it on to CheckCommand::Execute(): https://github.com/Icinga/icinga2/blob/eddd4c7bf7554a3700abe880781a7646703b7e5f/lib/icinga/apiactions.cpp#L784

Which in turn invokes the function in the execute attribute: https://github.com/Icinga/icinga2/blob/eddd4c7bf7554a3700abe880781a7646703b7e5f/lib/icinga/checkcommand.cpp#L13-L22

This can for example be PluginCheckTask::ScriptFunc() which starts a process and passes the check result to a callback function: https://github.com/Icinga/icinga2/blob/eddd4c7bf7554a3700abe880781a7646703b7e5f/lib/methods/pluginchecktask.cpp#L50-L52

Which then uses the check result like an output parameter:
https://github.com/Icinga/icinga2/blob/eddd4c7bf7554a3700abe880781a7646703b7e5f/lib/methods/pluginchecktask.cpp#L80-L86

So if I haven't overlooked anything, that seems to be a bug than can corrupt the last check result in memory.

Start by tracing /v1/actions/execute-command in lib/icinga/apiactions.cpp, then follow CheckCommand::Execute() in lib/icinga/checkcommand.cpp and PluginCheckTask::ScriptFunc() in lib/methods/pluginchecktask.cpp. Reproduce the action and inspect whether the existing last check result changes; done means confirming or disproving the suspected mutation and documenting the result or adding a regression test if the project’s tests support it.