pfgplots: axis with empty range

With the following MWE (I want to plot a bar chart with symbolic coordinates using pgfplots) I get an error that I have no idea how to fix:

Package pgfplots Warning: You have an axis with empty range (in direction x)

MWE:

documentclass[tikz]{standalone}
usepackage{pgfplots}
pgfplotsset{compat=newest}

begin{document}
begin{tikzpicture}
 begin{axis}[
    % axis on top,
    axis lines*=left,
    ymajorgrids,
    ybar,
    ymin=0, ymax=2000,
    xtick=data,
    ytick = {0,200,400,600,800,1000,1200,1400,1600,1800},
    bar width=0.1cm,
    enlarge x limits=0.15,
    enlarge y limits={upper, value=0.1},
    x tick label style={font=footnotesize,align=right,rotate=90},
    symbolic x coords={jan12,feb12,mar12,apr12,may12,jun12,jul12,aug12,sep12,oct12,nov12,dec12
  jan-13,feb-13,mar-13,apr-13,may-13,jun-13,jul-13,aug-13,sep-13,oct-13,nov-13,dec-13},
    ]
end{axis} 
end{tikzpicture}
end{document}

documentclass[tikz]{standalone}
usepackage{pgfplots}
pgfplotsset{compat=newest}

begin{document}
begin{tikzpicture}
 begin{axis}[
    % axis on top,
    axis lines*=left,
    ymajorgrids,
    ybar,
    ymin=0, ymax=2000,
    xmin=jan12, xmax=dec-13,
    xtick=data,
    ytick = {0,200,400,600,800,1000,1200,1400,1600,1800},
    bar width=0.1cm,
    enlarge x limits=0.15,
   enlarge y limits={upper, value=0.1},
    x tick label style={font=footnotesize,align=right,rotate=90},
    symbolic x coords={jan12,feb12,mar12,apr12,may12,jun12,jul12,aug12,sep12,oct12,nov12,dec12,
  jan-13,feb-13,mar-13,apr-13,may-13,jun-13,jul-13,aug-13,sep-13,oct-13,nov-13,dec-13},
    ]
end{axis} 
end{tikzpicture}
end{document}