use isWord() in the CryptaSymbols consumer #4141

Author: arnaud-m

src/main/java/cryptator/tree/CryptaSymbols.java

@@ -25,7 +25,7 @@ public CryptaSymbols() {
 
     @Override
     public void accept(ICryptaNode node, int numNode) {
-        if (!node.isInternalNode() && !node.isConstant()) {
+        if (!node.isWord()) {
             for (Character c : node.getWord()) {
                 letters.add(c);
             }