patch 8.0.0707: freeing wrong memory with certain autocommands

Problem:    Freeing wrong memory when manipulating buffers in autocommands.
            (James McCoy)
Solution:   Also set the w_s pointer if w_buffer was NULL.

src/ex_cmds.c

@@ -3968,8 +3968,8 @@ do_ecmd(
 		     * <VN> We could instead free the synblock
 		     * and re-attach to buffer, perhaps.
 		     */
-		    if (curwin->w_buffer != NULL
-			    && curwin->w_s == &(curwin->w_buffer->b_s))
+		    if (curwin->w_buffer == NULL
+			    || curwin->w_s == &(curwin->w_buffer->b_s))
 			curwin->w_s = &(buf->b_s);
 #endif
 		    curwin->w_buffer = buf;

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    707,
 /**/
     706,
 /**/