checker: fix returning optional empty map (#13113)

vlib/v/checker/containers.v

@@ -202,7 +202,7 @@ pub fn (mut c Checker) map_init(mut node ast.MapInit) ast.Type {
 		sym := c.table.sym(c.expected_type)
 		if sym.kind == .map {
 			info := sym.map_info()
-			node.typ = c.expected_type
+			node.typ = c.expected_type.clear_flag(.optional)
 			node.key_type = info.key_type
 			node.value_type = info.value_type
 			return node.typ

vlib/v/tests/option_empty_map_test.v

@@ -0,0 +1,13 @@
+fn opt() ?map[string]string {
+	return {}
+}
+
+fn test_option_empty_map() {
+	x := opt() or {
+		assert false
+		return
+	}
+
+	dump(x)
+	assert '$x' == '{}'
+}