Pluto ignores stop signals

Hi!

First, thanks for Pluto! :)

I've just run into this problem using Julia 1.4.2 and Pluto v0.11.0 in Ubuntu and Chrome.

Error deserializing a remote exception from worker 2
Remote(original) exception of type MethodError
Remote stacktrace : 
convert at ./missing.jl:69
convert at ./essentials.jl:310 (repeats 4 times)
Tuple at ./namedtuple.jl:110
convert at ./namedtuple.jl:105
fetch_formatted_result at /home/elin/.julia/packages/Pluto/zIhY2/src/runner/PlutoRunner.jl:34
top-level scope at /home/elin/.julia/packages/Pluto/zIhY2/src/evaluation/WorkspaceManager.jl:0
eval at ./boot.jl:331
#104 at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.4/Distributed/src/process_messages.jl:294
run_work_thunk at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.4/Distributed/src/process_messages.jl:79
macro expansion at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.4/Distributed/src/process_messages.jl:294 [inlined]
#103 at ./task.jl:358
Stacktrace:
 [1] remotecall_fetch(::Function, ::Distributed.Worker, ::Module, ::Vararg{Any,N} where N; kwargs::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.4/Distributed/src/remotecall.jl:390
 [2] remotecall_fetch(::Function, ::Distributed.Worker, ::Module, ::Vararg{Any,N} where N) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.4/Distributed/src/remotecall.jl:382
 [3] #remotecall_fetch#144 at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.4/Distributed/src/remotecall.jl:417 [inlined]
 [4] remotecall_fetch at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.4/Distributed/src/remotecall.jl:417 [inlined]
 [5] remotecall_eval at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.4/Distributed/src/macros.jl:240 [inlined]
 [6] eval_fetch_in_workspace(::Pluto.WorkspaceManager.Workspace, ::Expr, ::Base.UUID, ::Bool) at /home/elin/.julia/packages/Pluto/zIhY2/src/evaluation/WorkspaceManager.jl:153
 [7] eval_fetch_in_workspace at /home/elin/.julia/packages/Pluto/zIhY2/src/evaluation/WorkspaceManager.jl:119 [inlined]
 [8] run_single!(::Notebook, ::Cell) at /home/elin/.julia/packages/Pluto/zIhY2/src/evaluation/Run.jl:81
 [9] run_reactive!(::Pluto.ServerSession, ::Notebook, ::Pluto.NotebookTopology, ::Pluto.NotebookTopology, ::Array{Cell,1}; deletion_hook::Function) at /home/elin/.julia/packages/Pluto/zIhY2/src/evaluation/Run.jl:67
 [10] run_reactive! at /home/elin/.julia/packages/Pluto/zIhY2/src/evaluation/Run.jl:24 [inlined]
 [11] macro expansion at /home/elin/.julia/packages/Pluto/zIhY2/src/evaluation/Run.jl:11 [inlined]
 [12] (::Pluto.var"#68#69"{Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}},Pluto.ServerSession,Notebook,Array{Cell,1},Pluto.NotebookTopology,Pluto.NotebookTopology})() at ./task.jl:358[ Info: Tried to stop idle workspace - ignoring.
[ Info: Tried to stop idle workspace - ignoring.
[ Info: Tried to stop idle workspace - ignoring.
[ Info: Tried to stop idle workspace - ignoring.
[ Info: Tried to stop idle workspace - ignoring.
[ Info: Tried to stop idle workspace - ignoring.
[ Info: Tried to stop idle workspace - ignoring.
[ Info: Tried to stop idle workspace - ignoring.
[ Info: Tried to stop idle workspace - ignoring.
[ Info: Tried to stop idle workspace - ignoring.
[ Info: Tried to stop idle workspace - ignoring.
[ Info: Tried to stop idle workspace - ignoring.
[ Info: Tried to stop idle workspace - ignoring.
[ Info: Tried to stop idle workspace - ignoring.
[ Info: Tried to stop idle workspace - ignoring.
[ Info: Tried to stop idle workspace - ignoring.

Thanks