patch 8.2.3950: going beyond the end of the line with /\%V

Problem:    Going beyond the end of the line with /\%V.
Solution:   Check for valid column in getvcol().

src/charset.c

@@ -1240,10 +1240,15 @@ getvcol(
 	posptr = NULL;  // continue until the NUL
     else
     {
-	// Special check for an empty line, which can happen on exit, when
+	colnr_T i;
-	// ml_get_buf() always returns an empty string.
+
-	if (*ptr == NUL)
+	// In a few cases the position can be beyond the end of the line.
-	    pos->col = 0;
+	for (i = 0; i < pos->col; ++i)
+	    if (ptr[i] == NUL)
+	    {
+		pos->col = i;
+		break;
+	    }
 	posptr = ptr + pos->col;
 	if (has_mbyte)
 	    // always start on the first byte

src/testdir/test_regexp_latin.vim

@@ -1053,4 +1053,12 @@ func Test_using_visual_position()
   bwipe!
 endfunc
 
+func Test_using_invalid_visual_position()
+  " this was going beyond the end of the line
+  new
+  exe "norm 0o000\<Esc>0\<C-V>$s0"
+  /\%V
+  bwipe!
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -749,6 +749,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3950,
 /**/
     3949,
 /**/