title: Branching in Pyscipopt
body: <p>Branching on t_x21 led to this error</p>
  <blockquote>
  <p>[scip_branch.c:1061] ERROR: cannot branch on variable &lt;t_x21&gt; with fixed domain [-0,0]</p>
  </blockquote>
  <p>So, my guess as to why this did not work is that during presolving, SCIP fixed this variable to be 0 and hence it throws an error if we try to branch on it? Is this correct? (Also, this error occured after a restart)</p>
  <p><a href="https://github.com/scipopt/scip/blob/3d229190c1e6768d7c98641aca26d6e709a4f870/src/scip/scip_branch.c#L1061" rel="nofollow noreferrer">Link to scip_branch.c</a></p>