✨ feat: add new error message to show when no engines are selected (#227)

public/templates/search.html

@@ -45,6 +45,20 @@
             </div>
             <img src="./images/filter.png" alt="Image of a paper inside a funnel" />
         </div>
+        {{else}} {{#if noEnginesSelected}}
+        <div class="result_engine_not_selected">
+            <div class="description">
+                <p>
+                    No results could be fetched for your search "<span class="user_query">{{{this.pageQuery}}}</span>" .
+                </p>
+                <p class="description_paragraph">Dear user,</p>
+                <p class="description_paragraph">
+                    No results could be retrieved from the upstream search engines as no 
+                    upstream search engines were selected from the settings page. 
+                </p>
+            </div>
+            <img src="./images/no_selection.png" alt="Image of a white cross inside a red circle" />
+        </div>
         {{else}}
         <div class="result_not_found">
             <p>Your search - {{{this.pageQuery}}} - did not match any documents.</p>
@@ -56,7 +70,7 @@
             </ul>
             <img src="./images/no_results.gif" alt="Man fishing gif" />
         </div>
-        {{/if}} {{/if}} {{/if}}
+        {{/if}} {{/if}} {{/if}} {{/if}}
     </div>
     <div class="page_navigation">
         <button type="button" onclick="navigate_backward()">