added test for bugfixed empty! of RobinDict

Author: tozanski

test/test_robin_dict.jl

@@ -330,6 +330,9 @@ end
     @test h.count == 0
     @test h.idxfloor == 0
     @test length(h.hashes) == length(h.keys) == length(h.vals) == length0
+    for i=-1000:1000
+      @test !haskey(h, i)
+    end
 end
 
 @testset "ArgumentError" begin
@@ -424,4 +427,4 @@ end
         h[i] = i+1
     end
     check_invariants(h)
-end
+end