Do not check function call depth if no_function.

src/engine.rs

@@ -608,10 +608,13 @@ impl Engine {
         let native_only = hashes.1 == 0;
 
         // Check for stack overflow
+        #[cfg(not(feature = "no_function"))]
+        #[cfg(not(feature = "unchecked"))]
+        {
             if level > self.max_call_stack_depth {
                 return Err(Box::new(EvalAltResult::ErrorStackOverflow(pos)));
             }
-
+        }
         // First search in script-defined functions (can override built-in)
         if !native_only {
             if let Some(fn_def) = lib.get(&hashes.1) {