patch 9.0.1378: illegal memory access when using virtual editing

Problem:    Illegal memory access when using virtual editing.
Solution:   Make sure "startspaces" is not negative.
diff --git a/src/register.c b/src/register.c
index 461363b..f3df79c 100644
--- a/src/register.c
+++ b/src/register.c
@@ -1245,6 +1245,8 @@
 				// double-count it.
 				bd.startspaces = (ce - cs + 1)
 							  - oap->start.coladd;
+				if (bd.startspaces < 0)
+				    bd.startspaces = 0;
 				startcol++;
 			    }
 			}
diff --git a/src/testdir/test_virtualedit.vim b/src/testdir/test_virtualedit.vim
index 71cea42..edaae67 100644
--- a/src/testdir/test_virtualedit.vim
+++ b/src/testdir/test_virtualedit.vim
@@ -88,6 +88,16 @@
   set virtualedit=
 endfunc
 
+func Test_edit_special_char()
+  new
+  se ve=all
+  norm a0
+  sil! exe "norm o00000\<Nul>k<a0s"
+
+  bwipe!
+  set virtualedit=
+endfunc
+
 " Tests for pasting at the beginning, end and middle of a tab character
 " in virtual edit mode.
 func Test_paste_in_tab()
diff --git a/src/version.c b/src/version.c
index a9cf30e..c93499c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1378,
+/**/
     1377,
 /**/
     1376,