patch 8.2.2271: ml_get error when changing hidden buffer in Python

Problem:    ml_get error when changing hidden buffer in Python.
Solution:   Block updating folds. (closes #7598)
diff --git a/src/evalbuffer.c b/src/evalbuffer.c
index eabe626..376c1fe 100644
--- a/src/evalbuffer.c
+++ b/src/evalbuffer.c
@@ -807,6 +807,9 @@
 switch_buffer(bufref_T *save_curbuf, buf_T *buf)
 {
     block_autocmds();
+#ifdef FEAT_FOLDING
+    ++disable_fold_update;
+#endif
     set_bufref(save_curbuf, curbuf);
     --curbuf->b_nwindows;
     curbuf = buf;
@@ -821,6 +824,9 @@
 restore_buffer(bufref_T *save_curbuf)
 {
     unblock_autocmds();
+#ifdef FEAT_FOLDING
+    --disable_fold_update;
+#endif
     // Check for valid buffer, just in case.
     if (bufref_valid(save_curbuf))
     {