LibPDF: Parser::parse_header() return false if remaining bytes is zero

Author: https://github.com/bcoles
Commit: 6ccfa3e75e
Pull-request: https://github.com/SerenityOS/serenity/pull/10704
Issue: https://github.com/SerenityOS/serenity/issues/10702

Userland/Libraries/LibPDF/Parser.cpp

@@ -91,6 +91,8 @@ bool Parser::parse_header()
 {
     // FIXME: Do something with the version?
     m_reader.set_reading_forwards();
+    if (m_reader.remaining() == 0)
+        return false;
     m_reader.move_to(0);
     if (m_reader.remaining() < 8 || !m_reader.matches("%PDF-"))
         return false;