patch 8.2.0834: :drop command in terminal popup causes problems

Problem:    :drop command in terminal popup causes problems.
Solution:   Check for using a popup window. (closes #6151)
diff --git a/src/ex_cmds.c b/src/ex_cmds.c
index 9c55de3..777f149 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -6349,6 +6349,9 @@
     buf_T	*buf;
     tabpage_T	*tp;
 
+    if (ERROR_IF_POPUP_WINDOW || ERROR_IF_TERM_POPUP_WINDOW)
+	return;
+
     /*
      * Check if the first argument is already being edited in a window.  If
      * so, jump to that window.
diff --git a/src/testdir/test_popupwin.vim b/src/testdir/test_popupwin.vim
index 8c917bc..1e7d5ee 100644
--- a/src/testdir/test_popupwin.vim
+++ b/src/testdir/test_popupwin.vim
@@ -2445,6 +2445,9 @@
   call assert_fails('call feedkeys("gf", "xt")', 'E863:')
   call feedkeys("a\<C-U>", 'xt')
 
+  " Cannot escape from terminal window
+  call assert_fails('tab drop xxx', 'E863:')
+
   " Cannot open a second one.
   let termbuf2 = term_start(&shell, #{hidden: 1})
   call assert_fails('call popup_create(termbuf2, #{})', 'E861:')
diff --git a/src/version.c b/src/version.c
index 44f7f26..24a5767 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    834,
+/**/
     833,
 /**/
     832,