patch 8.2.4718: @@@ in the last line sometimes drawn in the wrong place

Problem:    @@@ in the last line sometimes drawn in the wrong place.
Solution:   Make sure the column is valid. (closes #10130)
diff --git a/src/testdir/dumps/Test_display_lastline_1.dump b/src/testdir/dumps/Test_display_lastline_1.dump
new file mode 100644
index 0000000..b0e34ea
--- /dev/null
+++ b/src/testdir/dumps/Test_display_lastline_1.dump
@@ -0,0 +1,10 @@
+>a+0&#ffffff0||+1&&|a+0&&@2| @69
+|a||+1&&|b+0&&@72
+|a||+1&&|b+0&&@26| @45
+|b||+1&&|~+0#4040ff13&| @71
+|b+0#0000000&||+1&&|~+0#4040ff13&| @71
+|b+0#0000000&||+1&&|~+0#4040ff13&| @71
+|b+0#0000000&||+1&&|~+0#4040ff13&| @71
+|@||+1#0000000&|~+0#4040ff13&| @71
+|<+3#0000000&| |[+1&&|N|o| |N|a|m|e|]| |[|+|]| @41|1|,|1| @11|A|l@1
+| +0&&@74
diff --git a/src/testdir/dumps/Test_display_lastline_2.dump b/src/testdir/dumps/Test_display_lastline_2.dump
new file mode 100644
index 0000000..2bd3309
--- /dev/null
+++ b/src/testdir/dumps/Test_display_lastline_2.dump
@@ -0,0 +1,10 @@
+>a+0&#ffffff0||+1&&|a+0&&@2| @69
+|a||+1&&|b+0&&@72
+|a||+1&&|b+0&&@26| @45
+|b||+1&&|~+0#4040ff13&| @71
+|b+0#0000000&||+1&&|~+0#4040ff13&| @71
+|b+0#0000000&||+1&&|~+0#4040ff13&| @71
+|b+0#0000000&||+1&&|~+0#4040ff13&| @71
+|@||+1#0000000&|~+0#4040ff13&| @71
+|<+3#0000000&| |[+1&&|N|o| |N|a|m|e|]| |[|+|]| @41|1|,|1| @11|A|l@1
+|:+0&&|s|e|t| |d|i|s|p|l|a|y|=|l|a|s|t|l|i|n|e| @53
diff --git a/src/testdir/dumps/Test_display_lastline_3.dump b/src/testdir/dumps/Test_display_lastline_3.dump
new file mode 100644
index 0000000..a0b6e09
--- /dev/null
+++ b/src/testdir/dumps/Test_display_lastline_3.dump
@@ -0,0 +1,10 @@
+>a+0&#ffffff0@2| @69||+1&&|a+0&&
+|b@72||+1&&|a+0&&
+|b@26| @45||+1&&|a+0&&
+|~+0#4040ff13&| @71||+1#0000000&|b+0&&
+|~+0#4040ff13&| @71||+1#0000000&|b+0&&
+|~+0#4040ff13&| @71||+1#0000000&|b+0&&
+|~+0#4040ff13&| @71||+1#0000000&|b+0&&
+|~+0#4040ff13&| @71||+1#0000000&|@+0#4040ff13&
+|[+3#0000000&|N|o| |N|a|m|e|]| |[|+|]| @41|1|,|1| @11|A|l@1| |<+1&&
+|:+0&&|1|0@1|w|i|n|c|m|d| |>| @62
diff --git a/src/testdir/dumps/Test_display_lastline_4.dump b/src/testdir/dumps/Test_display_lastline_4.dump
new file mode 100644
index 0000000..e34e7c7
--- /dev/null
+++ b/src/testdir/dumps/Test_display_lastline_4.dump
@@ -0,0 +1,10 @@
+>a+0&#ffffff0@2| @69||+1&&|a+0&&
+|b@72||+1&&|a+0&&
+|b@26| @45||+1&&|a+0&&
+|~+0#4040ff13&| @71||+1#0000000&|b+0&&
+|~+0#4040ff13&| @71||+1#0000000&|b+0&&
+|~+0#4040ff13&| @71||+1#0000000&|b+0&&
+|~+0#4040ff13&| @71||+1#0000000&|b+0&&
+|~+0#4040ff13&| @71||+1#0000000&|@+0#4040ff13&
+|[+3#0000000&|N|o| |N|a|m|e|]| |[|+|]| @41|1|,|1| @11|A|l@1| |<+1&&
+|:+0&&|s|e|t| |d|i|s|p|l|a|y|=|t|r|u|n|c|a|t|e| @53
diff --git a/src/testdir/test_display.vim b/src/testdir/test_display.vim
index a000521..f5c8dc5 100644
--- a/src/testdir/test_display.vim
+++ b/src/testdir/test_display.vim
@@ -372,5 +372,31 @@
   let &breakat=_breakat
 endfunc
 
+func Test_display_lastline()
+  CheckScreendump
+
+  let lines =<< trim END
+      call setline(1, ['aaa', 'b'->repeat(100)])
+      set display=truncate
+      vsplit
+      100wincmd <
+  END
+  call writefile(lines, 'XdispLastline')
+  let buf = RunVimInTerminal('-S XdispLastline', #{rows: 10})
+  call VerifyScreenDump(buf, 'Test_display_lastline_1', {})
+
+  call term_sendkeys(buf, ":set display=lastline\<CR>")
+  call VerifyScreenDump(buf, 'Test_display_lastline_2', {})
+
+  call term_sendkeys(buf, ":100wincmd >\<CR>")
+  call VerifyScreenDump(buf, 'Test_display_lastline_3', {})
+
+  call term_sendkeys(buf, ":set display=truncate\<CR>")
+  call VerifyScreenDump(buf, 'Test_display_lastline_4', {})
+
+  call StopVimInTerminal(buf)
+  call delete('XdispLastline')
+endfunc
+
 
 " vim: shiftwidth=2 sts=2 expandtab