patch 8.0.1672: error during completion causes command to be cancelled

Problem:    Error during completion causes command to be cancelled.
Solution:   Reset did_emsg before waiting for another character. (Tom M.)
diff --git a/src/testdir/test_cmdline.vim b/src/testdir/test_cmdline.vim
index 8755fbf..ff0756c 100644
--- a/src/testdir/test_cmdline.vim
+++ b/src/testdir/test_cmdline.vim
@@ -316,6 +316,17 @@
   call feedkeys(":\<C-\>etoupper(getline(1))\<CR>\<C-B>\"\<CR>", 'tx')
   call assert_equal('"ASDF.X /TMP/SOME VERYLONGWORD A;B-C*D ', @:)
   bwipe!
+
+  " Error while typing a command used to cause that it was not executed
+  " in the end.
+  new
+  try
+    call feedkeys(":file \<C-R>%Xtestfile\<CR>", 'tx')
+  catch /^Vim\%((\a\+)\)\=:E32/
+    " ignore error E32
+  endtry
+  call assert_equal("Xtestfile", bufname("%"))
+  bwipe!
 endfunc
 
 func Test_remove_char_in_cmdline()