patch 8.2.3470: crash with error in :catch and also in :finally

Problem:    Crash with error in :catch and also in :finally.
Solution:   Only discard an exception if there is one. (closes #8954)
diff --git a/src/testdir/test_trycatch.vim b/src/testdir/test_trycatch.vim
index 052fab7..ac12671 100644
--- a/src/testdir/test_trycatch.vim
+++ b/src/testdir/test_trycatch.vim
@@ -2273,6 +2273,18 @@
   call delete('XtestThrow')
 endfunc
 
+func ThisWillFail()
+  try
+    if x | endif
+  catch
+    for l in []
+  finally 
+endfunc
+
+func Test_error_in_catch_and_finally()
+  call assert_fails('call ThisWillFail()', ['E121:', 'E600:'])
+endfunc
+
 
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