Error in `report_invalidations` when invalidated method tree has no children

[ararslan]

The GitHub Actions job for checking invalidations failed on JuliaWeb/URIs.jl#63 with the following output:

(inv_total, inv_deps) = (1, 1)
[ Info: 1 methods invalidated for 1 functions
ERROR: LoadError: InexactError: Int64(NaN)
Stacktrace:
 [1] Int64
   @ ./float.jl:994 [inlined]
 [2] #3
   @ ~/.julia/packages/SnoopCompile/umz90/ext/SCPrettyTablesExt.jl:33 [inlined]
 [3] iterate
   @ ./generator.jl:48 [inlined]
 [4] _collect(c::Vector{Int64}, itr::Base.Generator{Vector{Int64}, SCPrettyTablesExt.var"#3#9"{Int64}}, ::Base.EltypeUnknown, isz::Base.HasShape{1})
   @ Base ./array.jl:811
 [5] collect_similar
   @ ./array.jl:720 [inlined]
 [6] map
   @ ./abstractarray.jl:3371 [inlined]
 [7] report_invalidations(io::IOContext{Base.PipeEndpoint}; invalidations::Vector{Any}, n_rows::Int64, process_filename::var"#1#2")
   @ SCPrettyTablesExt ~/.julia/packages/SnoopCompile/umz90/ext/SCPrettyTablesExt.jl:31
 [8] top-level scope
   @ ~/work/_temp/e7642433-c13a-41fb-861d-f3ad6083c2b6:13
in expression starting at /home/runner/work/_temp/e7642433-c13a-41fb-861d-f3ad6083c2b6:13

Full log here.

This appears to be happening because the invalidated method tree has no children.

(jl_zAHtQ6) pkg> status
Status `/private/var/folders/yw/ml6py_wx6vlffs_t678g81100000gp/T/jl_zAHtQ6/Project.toml`
  [08abe8d2] PrettyTables v2.4.0
  [aa65fe97] SnoopCompile v3.0.2
  [e2b509da] SnoopCompileCore v3.0.0
  [5c2747f8] URIs v1.5.1 `https://github.com/fredrikekre/URIs.jl#fe/tlv`

julia> using SnoopCompile, SnoopCompileCore, PrettyTables

julia> using SnoopCompile: countchildren

julia> invalidations = @snoop_invalidations using URIs
5-element Vector{Any}:
  MethodInstance for Artifacts.jointail(::Any, ::String)
 0
  Tuple{typeof(joinpath), Any, String}
  joinpath(uri::URI, parts::String...) @ URIs ~/.julia/packages/URIs/Fgl6j/src/URIs.jl:610
  "jl_method_table_insert"

julia> trees = reverse(invalidation_trees(invalidations))
1-element Vector{SnoopCompile.MethodInvalidations}:
 inserting joinpath(uri::URI, parts::String...) @ URIs ~/.julia/packages/URIs/Fgl6j/src/URIs.jl:610 invalidated:
   mt_backedges: 1: signature Tuple{typeof(joinpath), Any, String} triggered MethodInstance for Artifacts.jointail(::Any, ::String) (0 children)

julia> invs_per_method = map(countchildren, trees)
1-element Vector{Int64}:
 0

julia> sum_invs = sum(invs_per_method)
0

Since this is 0, populating the "Invalidations %" column in https://github.com/timholy/SnoopCompile.jl/blob/3de7217dc8ddd08b4048ba6614256a1f2e739bbb/ext/SCPrettyTablesExt.jl#L31-L34 errors, as 0/0 is NaN and Int(NaN) produces the InexactError as shown above.

An easy fix is to just not call Int and let the percent column be float-valued, but that seems like it could just be papering over an actual issue somewhere.