patch 8.1.1900: sign test fails in the GUI

Problem:    Sign test fails in the GUI.
Solution:   Catch and ignore the exception.
diff --git a/src/version.c b/src/version.c
index f91f07b..7dba139 100644
--- a/src/version.c
+++ b/src/version.c
@@ -766,6 +766,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1900,
+/**/
     1899,
 /**/
     1898,