vim-patch:8.0.1067: try/catch in timer does not prevent it from being stopped

Problem:    Using try/catch in timer does not prevent it from being stopped.
Solution:   Reset the exception context and use did_emsg instead of
            called_emsg.
e723c42836

src/nvim/testdir/test_timers.vim

@@ -189,6 +189,24 @@ func Test_input_in_timer()
   call assert_equal('hello', g:val)
 endfunc
 
+func FuncWithCaughtError(timer)
+  let g:call_count += 1
+  try
+    doesnotexist
+  catch
+    " nop
+  endtry
+endfunc
+
+func Test_timer_catch_error()
+  let g:call_count = 0
+  let timer = timer_start(10, 'FuncWithCaughtError', {'repeat': 4})
+  " Timer will not be stopped.
+  call WaitFor('g:call_count == 4')
+  sleep 50m
+  call assert_equal(4, g:call_count)
+endfunc
+
 func FeedAndPeek(timer)
   call test_feedinput('a')
   call getchar(1)