eval: let getreg() return valid list for an undefined register

vim-patch:7.4.1755
this prevents a crash when the list is used in setreg() later

src/nvim/version.c

@@ -69,6 +69,7 @@ static char *features[] = {
 
 // clang-format off
 static int included_patches[] = {
+  1755,
   1654,
   1652,
   1643,