[pstricks] How to cope with the error message

[cyrille.piatecki]

I need help to understand why I have an error here even if the box and 
the maths are perfectly displayed

Thanks


\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{inputenc}
\usepackage{pstricks, pstricks-add,pst-blur,pst-slpe}
\usepackage{xcolor}
\usepackage{amsmath}
%\psset{algebraic}

\begin{document}

\begin{center}
\psblurbox[fillstyle=slope,slopebegin=white,slopeend=gray,linestyle=none,shadow=true,blur=true]{%
\[
\left(C_0^\star, C_1^\star, C_2^\star\right)=
\underset{\{C_0, C_1, C_2\}}{\max}
\left\{U\left(C_0, C_1, C_2\right) \left|  W_0 = 
\sum_{t=0}^2\frac{R_t}{(1+r)^t}= 
\sum_{t=0}^2\frac{C_t}{(1+r)^t}\right.\right\}
  \]}
\end{center}