胚料bug修复，销售订单明细行路线修复，编程单下发优化

sf_mrs_connect/models/ftp_operate.py

@@ -25,15 +25,16 @@ class FtpController():
 
     # 下载目录下的文件
     def download_file_tree(self, target_dir, serverdir):
-        self.ftp.cwd(target_dir)  # 切换工作路径
         if not os.path.exists(serverdir):
             os.makedirs(serverdir)
-        remotenames = self.ftp.nlst()
-        for file in remotenames:
-            server = os.path.join(serverdir, file)
-            if file.find(".") != -1:
-                self.download_file(server, file)
-        return
+            self.ftp.cwd(target_dir)  # 切换工作路径
+            remotenames = self.ftp.nlst()
+            for file in remotenames:
+                server = os.path.join(serverdir, file)
+                if file.find(".") != -1:
+                    self.download_file(server, file)
+        else:
+            return
 
     # 下载指定目录下的指定文件
     def download_file(self, serverfile, remotefile):