Update

Author: odow

src/Utilities/universalfallback.jl

@@ -486,8 +486,10 @@ function MOI.get(
     listattr::MOI.ListOfVariableAttributesSet,
 )
     list = MOI.get(uf.model, listattr)
-    for attr in keys(uf.varattr)
-        push!(list, attr)
+    for (attr, dict) in uf.varattr
+        if !isempty(dict)
+            push!(list, attr)
+        end
     end
     return list
 end

test/Utilities/universalfallback.jl

@@ -103,6 +103,7 @@ function _test_Optimizer_Model_attributes(
     @test MOI.get(uf, list) == [attr]
     MOI.set(uf, attr, nothing)
     @test isempty(MOI.get(uf, list))
+    MOI.set(uf, attr, 0)
     return
 end