patch 9.0.1995: Invalid memory access with empty 'foldexpr'

Problem:  Invalid memory access when 'foldexpr' returns empty string.
Solution: Check for NUL.

closes: #13293

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: zeertzjq <zeertzjq@outlook.com>
diff --git a/src/version.c b/src/version.c
index 057cae5..ce13dcc 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1995,
+/**/
     1994,
 /**/
     1993,