patch 8.1.0019: error when defining a Lambda with index of a function result

Problem:    Error when defining a Lambda with index of a function result.
Solution:   When not evaluating an expression and skipping a function call,
            set the return value to VAR_UNKNOWN.
diff --git a/src/version.c b/src/version.c
index 1f8cfef..b629933 100644
--- a/src/version.c
+++ b/src/version.c
@@ -762,6 +762,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    19,
+/**/
     18,
 /**/
     17,