fix some glitches related to fetching events to the list on every resume

app/src/main/kotlin/com/simplemobiletools/calendar/fragments/EventListFragment.kt

@@ -30,6 +30,7 @@ import java.util.*
 
 class EventListFragment : MyFragmentHolder(), RefreshRecyclerViewListener {
     private var FETCH_INTERVAL = 6 * MONTH_SECONDS
+    private var MIN_EVENTS_TRESHOLD = 30
 
     private var mEvents = ArrayList<Event>()
     private var minFetchedTS = 0
@@ -65,7 +66,6 @@ class EventListFragment : MyFragmentHolder(), RefreshRecyclerViewListener {
             use24HourFormat = use24Hour
             (mView.calendar_events_list.adapter as? EventListAdapter)?.toggle24HourFormat(use24HourFormat)
         }
-        wereInitialEventsAdded = true
     }
 
     override fun onPause() {
@@ -74,18 +74,25 @@ class EventListFragment : MyFragmentHolder(), RefreshRecyclerViewListener {
     }
 
     private fun checkEvents() {
+        if (!wereInitialEventsAdded) {
             minFetchedTS = DateTime().minusMonths(3).seconds()
             maxFetchedTS = DateTime().plusMonths(6).seconds()
+        }
+
         context!!.dbHelper.getEvents(minFetchedTS, maxFetchedTS) {
+            if (it.size >= MIN_EVENTS_TRESHOLD) {
                 receivedEvents(it, false)
-            if (it.size < 30) {
+            } else {
+                if (!wereInitialEventsAdded) {
                     minFetchedTS -= FETCH_INTERVAL
                     maxFetchedTS += FETCH_INTERVAL
+                }
                 context!!.dbHelper.getEvents(minFetchedTS, maxFetchedTS) {
                     mEvents = it
                     receivedEvents(mEvents, false, !wereInitialEventsAdded)
                 }
             }
+            wereInitialEventsAdded = true
         }
     }