patch 8.0.0988: warning from Covscan about using NULL pointer

Problem:    Warning from Covscan about using NULL pointer.
Solution:   Add extra check for NULL. (zdohnal)
diff --git a/src/fileio.c b/src/fileio.c
index f54fb84..87a46b1 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -1370,7 +1370,8 @@
 		 * Decrypt the read bytes.  This is done before checking for
 		 * EOF because the crypt layer may be buffering.
 		 */
-		if (cryptkey != NULL && size > 0)
+		if (cryptkey != NULL && curbuf->b_cryptstate != NULL
+								   && size > 0)
 		{
 		    if (crypt_works_inplace(curbuf->b_cryptstate))
 		    {
diff --git a/src/undo.c b/src/undo.c
index b913841..62963a9 100644
--- a/src/undo.c
+++ b/src/undo.c
@@ -921,7 +921,7 @@
     static int
 undo_flush(bufinfo_T *bi)
 {
-    if (bi->bi_buffer != NULL && bi->bi_used > 0)
+    if (bi->bi_buffer != NULL && bi->bi_state != NULL && bi->bi_used > 0)
     {
 	crypt_encode_inplace(bi->bi_state, bi->bi_buffer, bi->bi_used);
 	if (fwrite(bi->bi_buffer, bi->bi_used, (size_t)1, bi->bi_fp) != 1)
diff --git a/src/version.c b/src/version.c
index 6d2de86..83cb3d9 100644
--- a/src/version.c
+++ b/src/version.c
@@ -770,6 +770,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    988,
+/**/
     987,
 /**/
     986,