Fix Set on nil nested maps

accessors.go

@@ -235,7 +235,7 @@ func access(current any, selector string, value any, action accessAction) (any,
 			_, ok = curMSI[thisSel].(Map)
 		}
 
-		if (curMSI[thisSel] == nil || !ok) && len(indexes) == 0 && action == actionSet {
+		if len(indexes) == 0 && action == actionSet && (!ok || reflect.ValueOf(curMSI[thisSel]).IsNil()) {
 			// An overflowing bracket index is parsed as a map key. Do not
 			// replace an existing slice with a map to follow it.
 			if reflect.ValueOf(curMSI[thisSel]).Kind() == reflect.Slice && overflow.overflows(nextSel) {
@@ -272,6 +272,11 @@ func access(current any, selector string, value any, action accessAction) (any,
 				return nil, false
 			}
 		}
+		if action == actionSet {
+			if v := reflect.ValueOf(current); v.Kind() == reflect.Map && v.IsNil() {
+				return nil, false
+			}
+		}
 	}
 
 	if nextSel != "" {

accessors_test.go

@@ -154,6 +154,42 @@ func TestAccessorsAccessSetDeep(t *testing.T) {
 	assert.Equal(t, "Ryer", m.Get("name.last").Data())
 }
 
+func TestAccessorsAccessSetNilNestedMap(t *testing.T) {
+	for name, nested := range map[string]any{
+		"nil":     nil,
+		"map":     map[string]any(nil),
+		"objxMap": objx.Map(nil),
+	} {
+		t.Run(name, func(t *testing.T) {
+			m := objx.Map{"nested": nested}
+			m.Set("nested.answer", 42)
+			assert.Equal(t, 42, m.Get("nested.answer").Data())
+			assert.Equal(t, map[string]any{"answer": 42}, m["nested"])
+		})
+	}
+}
+
+func TestAccessorsAccessSetNilMapInSlice(t *testing.T) {
+	for name, items := range map[string]any{
+		"nil":              []any{nil},
+		"map":              []any{map[string]any(nil)},
+		"objxMap":          []any{objx.Map(nil)},
+		"typed map slice":  []map[string]any{nil},
+		"typed objx slice": []objx.Map{nil},
+	} {
+		t.Run(name, func(t *testing.T) {
+			m := objx.Map{"items": items}
+			m.Set("items[0].answer", 42)
+			assert.Nil(t, m.Get("items[0]").Data())
+		})
+	}
+}
+
+func TestAccessorsAccessSetNilMap(t *testing.T) {
+	var m objx.Map
+	assert.Panics(t, func() { m.Set("answer", 42) })
+}
+
 func TestAccessorsAccessSetDeepDeep(t *testing.T) {
 	m := objx.Map{
 		"one": objx.Map{