Adding plain text destroys nice shapes and shadows on tittle page - beamer Warsaw theme

Question

I am creating a presentation for defending my thesis and I needed to add the name of my supervisor to title page. I did it using code from here ... It works fine when I consider adding the plain text, but it destroys nice shape of the color frame and its shading which is under the title as default on title page of this theme. I know that by redefining the title page I somehow "turned off" these features but I would like to turn them on again since it looks good.

Here is my code (not sure whether it will work here):

\documentclass{beamer}
\mode<presentation> {
  \usetheme{Warsaw}
  %\setbeamercovered{transparent}
}

%\usepackage{ucs}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[slovak]{babel}
\usepackage{palatino}
\usepackage{graphicx}

\title{Aplikácia metódy združených asymptotických rozvojov vo finančnej matematike.}
\subtitle{Application of matched asymptotic expansions method in financial mathematics.} 
\author%[Author, Anders] % (optional, for multiple authors)
{Bc. Jozef Janočko}
\institute[Universities Here and There] % (optional)
{

  Fakulta matematiky, fyziky a informatiky\\
  Univerzita Komenského
 }

%{RNDr. Be\'{a}ta Stehl\'{i}kov\'{a}, PhD.}
%\subject{Computer Science}
\setbeamertemplate{title page}
{
  \vbox{}
  \vfill
  \begingroup
    \flushleft RNDr. Beáta Stehlíková, PhD.
    \vskip0.5em%
    \centering
    \begin{beamercolorbox}[sep=8pt,center]{title}
      \usebeamerfont{title}\inserttitle\par%
      \ifx\insertsubtitle\@empty%
      \else%
        \vskip0.25em%
        {\usebeamerfont{subtitle}\usebeamercolor[fg]{subtitle}\insertsubtitle\par}%
      \fi%     
    \end{beamercolorbox}%
    \vskip1em\par
    \begin{beamercolorbox}[sep=8pt,center]{author}
      \usebeamerfont{author}\insertauthor
    \end{beamercolorbox}
    \begin{beamercolorbox}[sep=8pt,center]{institute}
      \usebeamerfont{institute}\insertinstitute
    \end{beamercolorbox}
    \begin{beamercolorbox}[sep=8pt,center]{date}
      \usebeamerfont{date}\insertdate \\
    \end{beamercolorbox}\vskip0.5em
    {\usebeamercolor[fg]{titlegraphic}\inserttitlegraphic\par}
  \endgroup
  \vfill
} 
\begin{document}
\frame{\titlepage}


\end{document}

This is how it looks now:

This is how it looked before:

Answer 1

Is this the result you are looking for?

\documentclass{beamer}
\mode<presentation> {
  \usetheme{Warsaw}
  %\setbeamercovered{transparent}
}

%\usepackage{ucs}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[slovak]{babel}
\usepackage{palatino}
\usepackage{graphicx}

\title[short version for footline]{Aplikácia metódy združených asymptotických rozvojov vo finančnej matematike.}
\subtitle{Application of matched asymptotic expansions method in financial mathematics.} 
\author%[Author, Anders] % (optional, for multiple authors)
{Bc. Jozef Janočko}
\institute[Universities Here and There] % (optional)
{

  Fakulta matematiky, fyziky a informatiky\\
  Univerzita Komenského
 }

%{RNDr. Be\'{a}ta Stehl\'{i}kov\'{a}, PhD.}
%\subject{Computer Science}
\makeatletter
\setbeamertemplate{title page}
{
    \vbox{}
    \vfill
    \begingroup
    \flushleft RNDr. Beáta Stehlíková, PhD.   % NEW
    \vskip0.5em                                                             % NEW
    \centering
    \begin{beamercolorbox}[sep=8pt,center,colsep=-4bp,rounded=true,shadow=\beamer@themerounded@shadow]{title}
        \usebeamerfont{title}\inserttitle\par%
        \ifx\insertsubtitle\@empty%
        \else%
        \vskip0.25em%
        {\usebeamerfont{subtitle}\usebeamercolor[fg]{subtitle}\insertsubtitle\par}%
        \fi%     
    \end{beamercolorbox}%
    \vskip1em\par
    \begin{beamercolorbox}[sep=8pt,center,colsep=-4bp,rounded=true,shadow=\beamer@themerounded@shadow]{author}
        \usebeamerfont{author}\insertauthor
    \end{beamercolorbox}
    \begin{beamercolorbox}[sep=8pt,center,colsep=-4bp,rounded=true,shadow=\beamer@themerounded@shadow]{institute}
        \usebeamerfont{institute}\insertinstitute
    \end{beamercolorbox}
    \begin{beamercolorbox}[sep=8pt,center,colsep=-4bp,rounded=true,shadow=\beamer@themerounded@shadow]{date}
        \usebeamerfont{date}\insertdate
    \end{beamercolorbox}\vskip0.5em
    {\usebeamercolor[fg]{titlegraphic}\inserttitlegraphic\par}
    \endgroup
    \vfill
}
\makeatother

\begin{document}
\frame{\titlepage}
\end{document}