Log instead on fail on wrong constructor in Java binding.

GitOrigin-RevId: 9349a4ff31a3a362d8921aa34493468fdd9a21f4

td/generate/tl_writer_jni_cpp.cpp

@@ -476,7 +476,7 @@ std::string TD_TL_writer_jni_cpp::gen_fetch_switch_case(const tl::tl_combinator
 
 std::string TD_TL_writer_jni_cpp::gen_fetch_switch_end() const {
   return "    default:\n"
-         "      UNREACHABLE();\n"
+         "      LOG(WARNING) << \"Unknown constructor found\";\n"
          "      return nullptr;\n"
          "  }\n";
 }