Tested;
It will lead to this error:
WARNING: Error running HandleEvent script in CScriptObject at 17507140: ...mdata\faforever\repo\fa\lua\ui\game\construction.lua(2145): attempt to call method `GetEntityId' (a nil value) stack traceback: ...mdata\faforever\repo\fa\lua\ui\game\construction.lua(2145): in function `FormatData' ...mdata\faforever\repo\fa\lua\ui\game\construction.lua(1288): in function `OrderEnhancement' ...mdata\faforever\repo\fa\lua\ui\game\construction.lua(1531): in function <...mdata\faforever\repo\fa\lua\ui\game\construction.lua:1530> c:\programdata\faforever\repo\fa\lua\ui\uiutil.lua(873): in function `OnClick' c:\programdata\faforever\repo\fa\lua\ui\uiutil.lua(937): in function <c:\programdata\faforever\repo\fa\lua\ui\uiutil.lua:933> c:\programdata\faforever\repo\fa\lua\ui\uiutil.lua(797): in function <c:\programdata\faforever\repo\fa\lua\ui\uiutil.lua:788>:GetEntityId() is called on the destroyed commander.