Fix bug introduced in return-handling refactor

(cherry picked from commit f8be17d362e51ff9f56f3e76e6776f9012c168f5)

worldedit-core/src/main/java/com/sk89q/worldedit/internal/expression/invoke/CompilingVisitor.java

@@ -678,10 +678,13 @@ class CompilingVisitor extends ExpressionBaseVisitor<MethodHandle> {
         // MH:oldResult,result = (ExecutionData)Double
 
         // Execute `oldResult` but ignore its return value, then execute result and return that.
-        // If `oldResult` (the old value) is `defaultResult`, it's bogus, so just skip it
+        // If either result is `defaultResult`, it's bogus, so just skip it
         if (oldResult == DEFAULT_RESULT) {
             return result;
         }
+        if (result == DEFAULT_RESULT) {
+            return oldResult;
+        }
         // Add a dummy Double parameter to the end
         // MH:dummyDouble = (ExecutionData, Double)Double
         MethodHandle dummyDouble = MethodHandles.dropArguments(