patch 9.0.0189: invalid memory access for text prop without highlight

Problem:    Invalid memory access for text prop without highlight.
Solution:   Check for a valid highlight ID.
diff --git a/src/version.c b/src/version.c
index 6675c3a..03a8091 100644
--- a/src/version.c
+++ b/src/version.c
@@ -736,6 +736,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    189,
+/**/
     188,
 /**/
     187,