remove empty bibliography

content/book/schmidt20_desig_high_perfor_mechat_third_revis_edition.md

@@ -454,7 +454,7 @@ The core of the control system is the _plant_, which is the physical system that
 <a id="table--tab:walk-control-loop"></a>
 <div class="table-caption">
   <span class="table-number"><a href="#table--tab:walk-control-loop">Table 3</a>:</span>
-  Symbols used in <a href="#orge4ef23e">3</a>
+  Symbols used in <a href="#orgda28b83">3</a>
 </div>
 
 | Symbol     | Meaning                              | Unit |