LibGUI: Allow comment(s) before first class marker in GML parser

This wasn't considered valid GML but now is:

    // This is a comment
    // This as well
    @Foo::Bar {}

1 files changed, 3 insertions, 0 deletions

diff --git a/Libraries/LibGUI/GMLParser.cpp b/Libraries/LibGUI/GMLParser.cpp
index bab0db544c..67df75479c 100644
--- a/Libraries/LibGUI/GMLParser.cpp
+++ b/Libraries/LibGUI/GMLParser.cpp
@@ -45,6 +45,9 @@ static Optional<JsonValue> parse_core_object(Queue<GMLToken>& tokens)
         return tokens.head().m_type;
     };
 
+    while (peek() == GMLToken::Type::Comment)
+        tokens.dequeue();
+
     if (peek() != GMLToken::Type::ClassMarker) {
         dbgln("Expected class marker");
         return {};