patch 8.1.1775: error message may be empty in filetype test

Problem:    Error message may be empty in filetype test.
Solution:   Use v:exception instead. (Daniel Hahler, closs #4744)
diff --git a/src/version.c b/src/version.c
index 8a3923e..1043275 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1775,
+/**/
     1774,
 /**/
     1773,