Add support for `empty` YANG leaf type

Change-Id: I87eafae9df9accdaa4579ace769996e70da6cb1c
diff --git a/src/yang_schema.cpp b/src/yang_schema.cpp
index 96fc744..6021cc5 100644
--- a/src/yang_schema.cpp
+++ b/src/yang_schema.cpp
@@ -246,6 +246,9 @@
         case LY_TYPE_BINARY:
             resType.emplace<yang::Binary>();
             break;
+        case LY_TYPE_EMPTY:
+            resType.emplace<yang::Empty>();
+            break;
         case LY_TYPE_ENUM:
             resType.emplace<yang::Enum>(enumValues(type));
             break;