fix: remove empty expression check in evaluate methods of ExpressionParser

Author: sharrlotte

src/java/mindustrytool/workflow/expressions/ExpressionParser.java

@@ -197,10 +197,6 @@ public <T> T evaluate(Class<T> type, String expr, Map<String, Object> variables)
                 }
             }
         }
-        if (stack.isEmpty()) {
-            throw new WorkflowError("Empty expression: " + expr);
-        }
-
         var result = stack.pop();
 
         if (result == null) {