title: Conformability error when using estfe with extended absvars
body: <p>I run a simple regression with <code>reghdfe</code> and would like to manually add three indicators to that.</p>
  <p>Let's first try with one indicator</p>
  <pre><code>sysuse auto.dta
  eststo m0: quietly reghdfe price turn, a(foreign)
  estadd local extended_absvars = &quot; a&quot;, replace
  ereturn list
  estfe m1, labels(a &quot;A&quot; b &quot;B&quot; c &quot;C&quot;)
  </code></pre>
  <p>that worked like a charm. Now, with three:</p>
  <pre><code>eststo m1: quietly reghdfe price turn, a(foreign)
  estadd local extended_absvars = &quot; a b c&quot;, replace
  ereturn list
  estfe m1, labels(a &quot;A&quot; b &quot;B&quot; c &quot;C&quot;)
  &gt;&gt; conformability error
  r(503);
  </code></pre>
  <p>The last lines from the stack trace are:</p>
  <pre><code>---------------------------------------- end estfe.FixAbsvars ----
  - if (&quot;`absvars'&quot;==&quot;&quot; &amp; &quot;`e(model'&quot;==&quot;fe&quot;) local absvars &quot;`e(ivar)'&quot;
  = if (&quot;0.a 0.b 0.c&quot;==&quot;&quot; &amp; &quot;&quot;==&quot;fe&quot;) local absvars &quot;&quot;
  - matrix `new' = J(1, `G', 0)
  = matrix __000002 = J(1 , 1, 0)
  - matrix colnames `new' = `absvars'
  = matrix colnames __000002 = 0.a 0.b 0.c
  conformability error
  ---------------------------------------- end estfe.AddOne ----
  local fe_list `fe_list' `absvars'
  }
  ---------------------------------------- end estfe.Add ----
  ---------------------------------------- end estfe ----
  </code></pre>
  <p>Why is this happening? Certainly if this was a common error I would have seen more about it when searching the web for the issue, but it appears unique? My version of <code>reghdfe</code> is <code>5.9.0</code> and <code>ftools</code> are installed.</p>