Vucic made a decision not to travel to Zagreb, he enclosed a letter with rationale

President Vucic was invited to the EPP Congress as the leader of the Serbian Progressive Party (SNS).
According to Blic, Vucic sent a letter to EPP President, Joseph Daul, containing rationale for his decision.
Here's integral version of the letter:
"Dear President Daul, my dear friend,
Let me thank you for inviting me to address the Congress of the European People's Party on November 20-21 in Zagreb.
Serbian Progressive Party prides itself on belonging to the family of European People's Parties and I would like to take this opportunity to thank you, dear President, for all you have done, both for Serbia's position in Europe and for the position of the Serbian Progressive Party in the most important family of European political parties. Also, please convey my congratulations to our party colleague, Ursula von der Leyen, on her election as Head of the European Commission, convinced that in these difficult times, she will show the whole of Europe why our European People's Party is the best, most serious and most responsible choice.
Dear friend,
Thank you for inviting me to personally address the Congress of the European People's Party in Zagreb on November 20th. To me, your call is a great honor and a demand for an even more responsible approach to solving many problems in the region in which we live. I want to inform you that I have prepared, I believe, a rather serious analysis of the developments in the region, as well as what we all should do together in the coming period. However, weeks ago, and I know that Jadranka Joksimovic informed you about it in the letter, a real media campaign was organized in almost all Croatian media opposing my arrival to Zagreb and Croatia. I would like to add that there are no real reasons...