patch 9.0.0018: going over the end of the typahead

Problem:    Going over the end of the typahead.
Solution:   Put a NUL after the typeahead.
diff --git a/src/term.c b/src/term.c
index 754ef82..7d7b84b 100644
--- a/src/term.c
+++ b/src/term.c
@@ -5393,6 +5393,7 @@
 	if (*tp == ESC && !p_ek && (State & MODE_INSERT))
 	    continue;
 
+	tp[len] = NUL;
 	key_name[0] = NUL;	// no key name found yet
 	key_name[1] = NUL;	// no key name found yet
 	modifiers = 0;		// no modifiers yet
diff --git a/src/testdir/test_mapping.vim b/src/testdir/test_mapping.vim
index ace6453..2927ba7 100644
--- a/src/testdir/test_mapping.vim
+++ b/src/testdir/test_mapping.vim
@@ -1715,4 +1715,14 @@
   call delete('Xtest_map_after_timed_out_nop')
 endfunc
 
+func Test_using_past_typeahead()
+  nnoremap :00 0
+  exe "norm :set \x80\xfb0=0\<CR>"
+  exe "sil norm :0\x0f\<C-U>\<CR>"
+
+  exe "norm :set \x80\xfb0=\<CR>"
+  nunmap :00
+endfunc
+
+
 " vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/version.c b/src/version.c
index 5d10909..6415b59 100644
--- a/src/version.c
+++ b/src/version.c
@@ -736,6 +736,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    18,
+/**/
     17,
 /**/
     16,