Fix bug when lx == ux

https://github.com/libigl/libigl/issues/658
Former-commit-id: aa066cfdea1bbfcef5b7ae5fbdade601e52a11a0

include/igl/mosek/mosek_linprog.cpp

@@ -79,9 +79,9 @@ IGL_INLINE bool igl::mosek::mosek_linprog(
     {
       if(lxj == uxj)
       {
-        k = MSK_BK_RA;
-      }else{
         k = MSK_BK_FX;
+      }else{
+        k = MSK_BK_RA;
       }
     }else if(isfinite(lxj))
     {