A panic against Juju 2.9.44 has be located whilst looking at production logs:
2023-09-06 18:55:55 CRITICAL juju.rpc server.go:557 panic running request {MethodCaller:0xc09b9dca50 transformErrors:0x2e864e0 hdr:{RequestId:588 Request:{Type:ModelManager Version:3 Id: Action:DumpModels} Error: ErrorCode: ErrorInfo:map[] Version:1}} with arg {Entities:[{Tag:model-b984d48f-94b8-4f96-8740-b201f8c7799c}] Simplified:true}: invalid user tag ""
goroutine 21810028 [running]:
runtime/debug.Stack()
/usr/local/go/src/runtime/debug/stack.go:24 +0x65
github.com/juju/juju/rpc.(*Conn).runRequest.func1()
/home/jenkins/workspace/build-juju/build/src/github.com/juju/juju/rpc/server.go:558 +0x7d
panic({0x4e611e0, 0xc05fd094c0})
/usr/local/go/src/runtime/panic.go:884 +0x213
github.com/juju/names/v4.NewUserTag({0x0, 0x0})
/home/jenkins/workspace/build-juju/build/src/github.com/juju/juju/vendor/github.com/juju/names/v4/user.go:102 +0xd4
github.com/juju/juju/state.newUserAccess(_, {{0x0, 0x0}, {0x0, 0x0}, {0x0, 0x0}, {0x0, 0x0}, {0x0, ...}, ...}, ...)
/home/jenkins/workspace/build-juju/build/src/github.com/juju/juju/state/useraccess.go:172 +0x73
github.com/juju/juju/state.NewControllerUserAccess(_, {{0x0, 0x0}, {0x0, 0x0}, {0x0, 0x0}, {0x0, 0x0}, {0x0, ...}, ...})
/home/jenkins/workspace/build-juju/build/src/github.com/juju/juju/state/useraccess.go:140 +0x26a
github.com/juju/juju/state.(*State).UserAccess(0xc0b9b58ef0?, {{0xc104955925?, 0x19?}, {0x0?, 0x0?}}, {0x6532a70, 0xc020ec02a0})
/home/jenkins/workspace/build-juju/build/src/github.com/juju/juju/state/useraccess.go:217 +0x48c
github.com/juju/juju/state.(*State).UserPermission(0x10?, {{0xc104955925?, 0x4e60f20?}, {0x0?, 0x7fd774836948?}}, {0x6532a70, 0xc020ec02a0})
/home/jenkins/workspace/build-juju/build/src/github.com/juju/juju/state/useraccess.go:151 +0x1b0
github.com/juju/juju/apiserver/common.GetPermission(0xc0e9101890, {{0xc104955925?, 0xc0e9101888?}, {0x0?, 0xc0e9101898?}}, {0x6532a70, 0xc020ec02a0})
/home/jenkins/workspace/build-juju/build/src/github.com/juju/juju/apiserver/common/permissions.go:70 +0x76
github.com/juju/juju/apiserver/common.HasPermission(0x10?, {0x6532ce0?, 0xc052992ce0}, {0x5c05b89, 0x9}, {0x6532a70, 0xc020ec02a0?})
/home/jenkins/workspace/build-juju/build/src/github.com/juju/juju/apiserver/common/permissions.go:49 +0x17c
github.com/juju/juju/apiserver.(*apiHandler).HasPermission(0xc0c0522de0, {0x5c05b89, 0x9}, {0x6532a70, 0xc020ec02a0})
/home/jenkins/workspace/build-juju/build/src/github.com/juju/juju/apiserver/root.go:718 +0x85
github.com/juju/juju/apiserver/facades/client/modelmanager.NewModelManagerAPI({0x657e510?, 0xc0a42f5500}, {0x657e510?, 0xc0a42f5640}, {0x64f0a60?, 0xc08561e980}, {0x64e6ca0?, 0xc0a42f54c0}, 0x5e54b98, {0x6523230, ...}, ...)
/home/jenkins/workspace/build-juju/build/src/github.com/juju/juju/apiserver/facades/client/modelmanager/modelmanager.go:219 +0x12d
github.com/juju/juju/apiserver/facades/client/modelmanager.newFacadeV9({0x6565128, 0xc09b9dcab0})
/home/jenkins/workspace/build-juju/build/src/github.com/juju/juju/apiserver/facades/client/modelmanager/register.go:86 +0x605
github.com/juju/juju/apiserver/facades/client/modelmanager.newFacadeV8(...)
/home/jenkins/workspace/build-juju/build/src/github.com/juju/juju/apiserver/facades/client/modelmanager/register.go:101
github.com/juju/juju/apiserver/facades/client/modelmanager.newFacadeV7({0x6565128?, 0xc09b9dcab0?})
/home/jenkins/workspace/build-juju/build/src/github.com/juju/juju/apiserver/facades/client/modelmanager/register.go:110 +0x27
github.com/juju/juju/apiserver/facades/client/modelmanager.newFacadeV6(...)
/home/jenkins/workspace/build-juju/build/src/github.com/juju/juju/apiserver/facades/client/modelmanager/register.go:119
github.com/juju/juju/apiserver/facades/client/modelmanager.newFacadeV5({0x6565128?, 0xc09b9dcab0?})
/home/jenkins/workspace/build-juju/build/src/github.com/juju/juju/apiserver/facades/client/modelmanager/register.go:128 +0x27
github.com/juju/juju/apiserver/facades/client/modelmanager.newFacadeV4(...)
/home/jenkins/workspace/build-juju/build/src/github.com/juju/juju/apiserver/facades/client/modelmanager/register.go:137
github.com/juju/juju/apiserver/facades/client/modelmanager.newFacadeV3({0x6565128?, 0xc09b9dcab0?})
/home/jenkins/workspace/build-juju/build/src/github.com/juju/juju/apiserver/facades/client/modelmanager/register.go:146 +0x27
github.com/juju/juju/apiserver/facades/client/modelmanager.Register.func2({0x6565128?, 0xc09b9dcab0?})
/home/jenkins/workspace/build-juju/build/src/github.com/juju/juju/apiserver/facades/client/modelmanager/register.go:26 +0x25
github.com/juju/juju/apiserver.(*apiRoot).FindMethod.func1({0x0?, 0xc0cacf6d58?})
/home/jenkins/workspace/build-juju/build/src/github.com/juju/juju/apiserver/root.go:380 +0x338
github.com/juju/juju/apiserver.(*srvCaller).Call(0xc09b9dca50, {0x6539808, 0xc0ee910910}, {0x0?, 0x4?}, {0x5416160?, 0xc05f876580?, 0x40ab2d?})
/home/jenkins/workspace/build-juju/build/src/github.com/juju/juju/apiserver/root.go:184 +0x5e
github.com/juju/juju/rpc.(*Conn).runRequest(0xc04ee40780, {{0x65231d0, 0xc09b9dca50}, 0x5e54128, {0x24c, {{0xc116350c24, 0xc}, 0x3, {0x0, 0x0}, ...}, ...}}, ...)
/home/jenkins/workspace/build-juju/build/src/github.com/juju/juju/rpc/server.go:571 +0x1b6
created by github.com/juju/juju/rpc.(*Conn).handleRequest
/home/jenkins/workspace/build-juju/build/src/github.com/juju/juju/rpc/server.go:475 +0x685
