title: Error while viewing a pdf file using latex-suite in macVim
body: <p>I get this error after typing lv for viewing the pdf file in macVim. 
  Note: after compiling it (with ll) without any problem:</p>
  
  <p>Error detected while processing function Tex_ViewLaTeX:
  line   34:
  E121: Undefined variable: s:viewer
  E116: Invalid arguments for function strlen(s:viewer)
  E15: Invalid expression: strlen(s:viewer)
  line   39:
  E121: Undefined variable: appOpt
  E15: Invalid expression: 'open '.appOpt.s:viewer.' $<em>.'.s:target
  line   79:
  E121: Undefined variable: execString
  E116: Invalid arguments for function substitute(execString, '\V$</em>', mainfname, 'g
  ')
  E15: Invalid expression: substitute(execString, '\V$*', mainfname, 'g')
  line   80:
  E121: Undefined variable: execString
  E116: Invalid arguments for function Tex_Debug
  line   82:
  E121: Undefined variable: execString
  E15: Invalid expression: 'silent! !'.execString</p>
  
  <p>I already defined the pdf viewer in the .vimrc file with 
  let g:Tex_ViewRule_pdf = 'open -a Preview'</p>
  
  <p>Also tried treating macUnix as Unix with
  let g:Tex_TreatMacViewerAsUNIX = 1</p>