fix: only return null if there are no lines

Evaluator.cs

@@ -25,11 +25,13 @@ public class Evaluator {
             }
         }
 
-        if (!this.Lines.TryGetValue(evaluation, out var currentLines)) {
-            return null;
+        if (this.Lines.TryGetValue(evaluation, out var currentLines)) {
+            lines.AddRange(currentLines);
         }
 
-        lines.AddRange(currentLines);
+        if (lines.Count == 0) {
+            return null;
+        }
 
         var template = Random.Shared.GetItems(lines.ToArray(), 1)[0];
         var line = new SeStringBuilder();