fix: autocompletion sometimes throwing an error when there are no sug…

…gestions

Fix the bug where we get this uncaught error:

> TypeError: reduce of empty array with no initial value

src/js/SchemaTextCompleter.js

@@ -178,7 +178,7 @@ export class SchemaTextCompleter {
                 }
               }
               return last
-            })
+            }, null)
             if (typeof option === 'string') {
               if (currentSuggestions[option]?.refs?.length) {
                 const mergedSuggestions = {}