YAwn: Fix memory leak

doc/news/_preparation_next_release.md

@@ -116,6 +116,7 @@ and be assured that you can safely set a path value to the key. A more detailed
 
 - The plugin now handles comments at the end of a file properly. *(René Schwaiger)*
 - We improved the syntax error messages of the plugin. *(René Schwaiger)*
+- We fixed a memory leak that occurred, if a YAML file contained syntax errors. *(René Schwaiger)*
 
 ### YAy PEG
 
@@ -142,7 +143,7 @@ The new plugin [YAy PEG](https://www.libelektra.org/plugins/yaypeg) parses a sub
   - [`resolver`](https://www.libelektra.org/plugins/resolver)
 
   reported on FreeBSD. *(René Schwaiger)*
-- The [`resolver` plugin](/src/plugins/resolver) and its tests now better support `KDB_DB_SYSTEM` and `KDB_DB_SPEC` paths 
+- The [`resolver` plugin](/src/plugins/resolver) and its tests now better support `KDB_DB_SYSTEM` and `KDB_DB_SPEC` paths
   using `~` to refer to a home directory. *(Klemens Böswirth)*
 - If `KDB_DB_SYSTEM` is set to a relative path, it is now treated as relative to `CMAKE_INSTALL_PREFIX`. This ensures that
   `KDB_DB_SYSTEM` actually points to the same location no matter the current working directory. *(Klemens Böswirth)*

src/plugins/yawn/convert.cpp

@@ -201,7 +201,11 @@ int addToKeySet (CppKeySet & keySet, CppKey & parent, string const & filename)
 
 	parser.parse (nextToken, syntaxError, nullptr, nullptr, &root, &ambiguousOutput);
 
-	if (handleErrors (ambiguousOutput, errorListener, filename, grammar, parent) < 0) return -1;
+	if (handleErrors (ambiguousOutput, errorListener, filename, grammar, parent) < 0)
+	{
+		yaep::free_tree (root, nullptr, nullptr);
+		return -1;
+	}
 
 	Listener listener{ parent };
 	walk (listener, root);