patch 7.4.1081

Problem:    No test for what previously caused a crash.
Solution:   Add test for unletting errmsg.

src/testdir/test_unlet.vim

@@ -7,6 +7,12 @@ func Test_read_only()
   catch
     call assert_true(v:exception =~ ':E795:')
   endtry
+  try
+    " this caused a crash
+    unlet errmsg
+  catch
+    call assert_true(v:exception =~ ':E795:')
+  endtry
 endfunc
 
 func Test_existing()

src/version.c

@@ -741,6 +741,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1081,
 /**/
     1080,
 /**/