patch 8.2.0243: insufficient code coverage for ex_docmd.c functions

Problem:    Insufficient code coverage for ex_docmd.c functions.
Solution:   Add more tests. (Yegappan Lakshmanan, closes #5618)
diff --git a/src/testdir/test_quickfix.vim b/src/testdir/test_quickfix.vim
index 3f4574a..cc5ee80 100644
--- a/src/testdir/test_quickfix.vim
+++ b/src/testdir/test_quickfix.vim
@@ -2725,10 +2725,6 @@
   call assert_equal(0, getbufinfo('Xtestfile1')[0].loaded)
   call assert_equal([], getbufinfo('Xtestfile2'))
 
-  " Test with the last search pattern not set
-  call test_clear_search_pat()
-  call assert_fails('Xvimgrep // *', 'E35:')
-
   call delete('Xtestfile1')
   call delete('Xtestfile2')
 endfunc
@@ -2754,6 +2750,21 @@
   set noincsearch
 endfunc
 
+" Test vimgrep with the last search pattern not set
+func Test_vimgrep_with_no_last_search_pat()
+  let lines =<< trim [SCRIPT]
+    call assert_fails('vimgrep // *', 'E35:')
+    call writefile(v:errors, 'Xresult')
+    qall!
+  [SCRIPT]
+  call writefile(lines, 'Xscript')
+  if RunVim([], [], '--clean -S Xscript')
+    call assert_equal([], readfile('Xresult'))
+  endif
+  call delete('Xscript')
+  call delete('Xresult')
+endfunc
+
 func XfreeTests(cchar)
   call s:setup_commands(a:cchar)