fix: Cannot show compilation units under the default package (#447)

Author: jdneo

jdtls.ext/com.microsoft.jdtls.ext.core/src/com/microsoft/jdtls/ext/core/model/Trie.java

@@ -33,6 +33,9 @@ public Set<TrieNode<T>> getAllNodes() {
 
     public void insert(String name, T value) {
         if (StringUtils.isBlank(name)) {
+            // default package
+            root.value = value;
+            allNodes.add(root);
             return;
         }