patch 8.1.0426: accessing invalid memory in SmcOpenConnection()

Problem:    Accessing invalid memory in SmcOpenConnection().
Solution:   Reduce size of errorstring by one. (Dominique Pelle, closes #3469)
diff --git a/src/testdir/test_startup.vim b/src/testdir/test_startup.vim
index 4a296ec..6f06ab8 100644
--- a/src/testdir/test_startup.vim
+++ b/src/testdir/test_startup.vim
@@ -272,7 +272,7 @@
 " Test the -V[N]{filename} argument to set the 'verbose' option to N
 " and set 'verbosefile' to filename.
 func Test_V_file_arg()
-  if RunVim([], [], ' --clean -X -V2Xverbosefile -c "set verbose? verbosefile?" -cq')
+  if RunVim([], [], ' --clean -V2Xverbosefile -c "set verbose? verbosefile?" -cq')
     let out = join(readfile('Xverbosefile'), "\n")
     call assert_match("sourcing \"$VIMRUNTIME[\\/]defaults\.vim\"\n", out)
     call assert_match("\n  verbose=2\n", out)