LibPDF: Permit comments at the end of a stream

Userland/Libraries/LibPDF/Parser.cpp

@@ -519,6 +519,8 @@ PDFErrorOr<Vector<Operator>> Parser::parse_operators()
 
     while (!m_reader.done()) {
         parse_comment();
+        if (m_reader.done())
+            break;
         auto ch = m_reader.peek();
         if (is_operator_char_start(ch)) {
             auto operator_start = m_reader.offset();