patch 8.2.3962: build fails for missing error message

Problem:    Build fails for missing error message.
Solution:   Add changes in missed file.
diff --git a/src/regexp_bt.c b/src/regexp_bt.c
index f631741..8d94358 100644
--- a/src/regexp_bt.c
+++ b/src/regexp_bt.c
@@ -1392,7 +1392,8 @@
       case Magic(')'):
 	if (one_exactly)
 	    EMSG_ONE_RET_NULL;
-	IEMSG_RET_NULL(_(e_internal));	// Supposed to be caught earlier.
+	// Supposed to be caught earlier.
+	IEMSG_RET_NULL(_(e_internal_error_in_regexp));
 	// NOTREACHED
 
       case Magic('='):
diff --git a/src/version.c b/src/version.c
index 945d147..bb73823 100644
--- a/src/version.c
+++ b/src/version.c
@@ -750,6 +750,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3962,
+/**/
     3961,
 /**/
     3960,