patch 8.2.4782: accessing freed memory

Problem:    Accessing freed memory.
Solution:   Clear evalarg after checking for trailing characters.
            (issue #10218)

src/testdir/test_lambda.vim

@@ -1,6 +1,7 @@
 " Test for lambda and closure
 
 source check.vim
+import './vim9.vim' as v9
 
 func Test_lambda_feature()
   call assert_equal(1, has('lambda'))
@@ -54,6 +55,21 @@ func Test_lambda_with_timer()
   call assert_true(s:n > m)
 endfunc
 
+func Test_lambda_vim9cmd_linebreak()
+  CheckFeature timers
+
+  let lines =<< trim END
+      vim9cmd call timer_start(10, (x) => {
+          # comment
+          g:result = 'done'
+         })
+  END
+  call v9.CheckScriptSuccess(lines)
+  sleep 50m
+  call assert_equal('done', g:result)
+  unlet g:result
+endfunc
+
 func Test_lambda_with_partial()
   let l:Cb = function({... -> ['zero', a:1, a:2, a:3]}, ['one', 'two'])
   call assert_equal(['zero', 'one', 'two', 'three'], l:Cb('three'))