patch 8.2.4919: can add invalid bytes with :spellgood

Problem:    Can add invalid bytes with :spellgood.
Solution:   Check for a valid word string.
diff --git a/src/version.c b/src/version.c
index f949dd6..c4f5655 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4919,
+/**/
     4918,
 /**/
     4917,