ReaderDictionary: fix possible crash with Wikipedia

Also reword some "...canceled" to "...interrupted"
for consistency.

frontend/apps/reader/modules/readerdictionary.lua

@@ -914,7 +914,7 @@ function ReaderDictionary:showDict(word, results, box, link)
     self:dismissLookupInfo()
     if results and results[1] then
         UIManager:show(self.dict_window)
-        if not results.lookup_cancelled and ffiUtil.getDuration(self._lookup_start_ts) > self.quick_dismiss_before_delay then
+        if not results.lookup_cancelled and self._lookup_start_ts and ffiUtil.getDuration(self._lookup_start_ts) > self.quick_dismiss_before_delay then
             -- If the search took more than a few seconds to be done, discard
             -- queued and coming up events to avoid a voluntary dismissal
             -- (because the user felt the result would not come) to kill the

frontend/apps/reader/modules/readerwikipedia.lua

@@ -502,7 +502,7 @@ function ReaderWikipedia:lookupWikipedia(word, is_sane, box, get_fullpage, force
         -- dummy results
         local definition
         if lookup_cancelled then
-            definition = _("Wikipedia request canceled.")
+            definition = _("Wikipedia request interrupted.")
         elseif ok then
             definition = no_result_text
         else

frontend/ui/widget/dictquicklookup.lua

@@ -430,7 +430,7 @@ function DictQuickLookup:update()
                                             })
                                         else
                                             UIManager:show(InfoMessage:new{
-                                                text = _("Saving Wikipedia article failed or canceled."),
+                                                text = _("Saving Wikipedia article failed or interrupted."),
                                             })
                                         end
                                     end)