title: "object not found" error when making forecast with a fitted "tslm" model
body: <p>I am trying to implement leave-one-out cross-validation for my time series but got stumbled against a forecasting error.</p>
  
  <pre><code>library('forecast')
  
  data_aero &lt;- c(579, 624, 651, 687,  745,  753,  844,  965, 1076, 1078, 1107)
  data_railway &lt;-c(1417, 1507, 1696, 1831, 1985, 1506, 1854, 2059, 2104, 1932, 1778)
  
  
  data.ts &lt;- ts(data=data.frame(aero = data_aero, railway = data_railway),  start = 2004)
  
  st &lt;- 2003
  limit &lt;- 2013
  en &lt;- 2014
  
  data.ts.train &lt;- window(data.ts, start=st, end=limit)
  data.ts.test  &lt;- window(data.ts, start=limit+1, end=en)
  
  
  m &lt;- tslm(aero~railway, data=data.ts.train)
  </code></pre>
  
  <p>Till here everything is fine, but if I do</p>
  
  <pre><code>forecast(m, h=1)
  </code></pre>
  
  <p>I get an error</p>
  
  <pre><code>Error in eval(expr, envir, enclos) : object 'railway' not found
  </code></pre>