fix(src): avoid possible infinite loop in LoadAll().

Leave at first empty root.

Signed-off-by: Federico Di Pierro <nierro92@gmail.com>

src/parse.cpp

@@ -53,7 +53,7 @@ std::vector<Node> LoadAll(std::istream& input) {
   Parser parser(input);
   while (true) {
     NodeBuilder builder;
-    if (!parser.HandleNextDocument(builder)) {
+    if (!parser.HandleNextDocument(builder) || builder.Root().IsNull()) {
       break;
     }
     docs.push_back(builder.Root());