Small update to DoString for stack discipline

wrapper.go

@@ -70,9 +70,24 @@ func (s *State) DoString(str string) error {
 
 	if s.safeStack {
 		return stackGuardErr(s, func() error {
-			return s.safeCall(func() C.int {
-				return C.do_string(s.L, cstr)
-			})
+			// Save the current stack size
+			initialTop := s.GetTop()
+
+			// Execute the string
+			status := C.do_string(s.L, cstr)
+			if status != 0 {
+				// In case of error, get error message from stack
+				errMsg := s.ToString(-1)
+				s.SetTop(initialTop) // Restore stack
+				return &LuaError{
+					Code:    int(status),
+					Message: errMsg,
+				}
+			}
+
+			// Return values are now on the stack above initialTop
+			// We don't pop them as they may be needed by the caller
+			return nil
 		})
 	}