beamer - error = there's no line here to end - \end{frame}

\documentclass[english,10pt]{beamer}
\usetheme{JuanLesPins}
\setbeamercovered{transparent}
\definecolor{bleuklein}{rgb}{0.30,0.10,0.95}
\usecolortheme[named=bleuklein]{structure}

\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage[french]{babel}
\setbeamersize{text margin left = 2mm, % normalement c'est 1 cm
    text margin right = 2mm % normalement c'est 1 cm}
\usepackage{color}
\usepackage{xcolor}
\usepackage{pgf}
\usepackage{tikz}
\usepackage{graphicx}
\DeclareGraphicsExtensions{.jpg,.pdf,.png}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{url}
\usepackage{setspace}
\usepackage{gensymb}
\usepackage{mathrsfs}
\usepackage{chemfig}
\usepackage{pgfplots}
\usepackage{siunitx}
\usepackage{booktabs}
\usepackage{tabularx}
\usepackage{array}
\usepackage{ragged2e, makecell, mhchem}
\usepackage{fancyhdr}
\pagestyle{fancy}
\pagestyle{empty}
\usepackage{caption}

\begin{document}

\begin{frame}[shrink=20]
 \begin{center} 
 \begin{figure}
    \includegraphics[clip,angle=90,scale=0.10]{images/quadrant.jpg}
    \caption{Classification of materials based on the electric permittivity $\epsilon_{r}$ ans magnetic permeability $\mu_{r}$}
 \end{figure}

 \begin{figure}
    \includegraphics[clip,scale=0.10]{images/loi_snell.jpg}
    \caption{Schematic of refraction of ordinary material medium (A) and negative index material medium (B)}
 \end{figure}
\end{center}        
\end{frame}

\begin{frame}[shrink=20]
Molar mass : 188k. PS : 135k; P2VP : 53k in PGMEA

\begin{figure}
    \includegraphics[clip,scale=0.15]{images/psp2vp.jpg}
    \caption{block copolymer PS-b-P2VP}\\

    \includegraphics[clip,scale=0.15]{images/PGMEA.png}
    \caption{PGMEA}
\end{figure}
\end{frame}
\end{document}