patch 9.1.1406: crash when importing invalid tuple

Problem:  crash when importing invalid tuple
          (Yang LUO, Yanju Chen)
Solution: set type to VAR_UNKNOWN, so that it isn't freed
          (Yegappan Lakshmanan)

closes: #17362

Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_tuple.vim b/src/testdir/test_tuple.vim
index e767851..45f730d 100644
--- a/src/testdir/test_tuple.vim
+++ b/src/testdir/test_tuple.vim
@@ -1586,6 +1586,17 @@
         \ 'E121: Undefined variable: pat'])
 endfunc
 
+" The following used to crash Vim
+func Test_import_invalid_tuple()
+  let lines =<< trim END
+    imp(",G0}11*f[+\x","#|
+  END
+  new
+  call setline(1, lines)
+  call assert_fails('source', 'E114: Missing double quote: "#|')
+  bw!
+endfunc
+
 " Test for add() with a tuple
 func Test_tuple_add()
   let lines =<< trim END