patch 8.0.0270: may get ml_get error when :rubydo deletes lines

Problem:    May get ml_get error when :rubydo deletes lines or switches to
            another buffer. (Nikolai Pavlov, issue #1421)
Solution:   Check the buffer and line every time.
diff --git a/src/version.c b/src/version.c
index 476074f..44e5b6f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    270,
+/**/
     269,
 /**/
     268,