Fix _addcounts_radix_sort for empty input array (#706)

Author: bosonbaas

src/counts.jl

@@ -336,6 +336,7 @@ const BaseRadixSortSafeTypes = Union{Int8, Int16, Int32, Int64, Int128,
 radixsort_safe(::Type{T}) where T = T<:BaseRadixSortSafeTypes
 
 function _addcounts_radix_sort_loop!(cm::Dict{T}, sx::AbstractArray{T}) where T
+    isempty(sx) && return cm
     last_sx = sx[1]
     tmpcount = get(cm, last_sx, 0) + 1
 

test/counts.jl

@@ -108,6 +108,9 @@ cm_any_itr = countmap((i for i in xx))
 @test cm_any_itr isa Dict{Any,Int} # no knowledge about type
 @test cm_missing == cm
 
+# with empty array
+@test countmap(Int[]) == Dict{Int, Int}()
+
 # testing the radixsort-based addcounts
 xx = repeat([6, 1, 3, 1], outer=100_000)
 cm = Dict{Int, Int}()