make sure we try updaing the viewpager from the UI thread after importing

app/src/main/kotlin/com/simplemobiletools/calendar/activities/MainActivity.kt

@@ -305,10 +305,12 @@ class MainActivity : SimpleActivity(), NavigationListener {
     private fun importEventsDialog(path: String) {
         ImportEventsDialog(this, path) {
             if (it) {
+                runOnUiThread {
                     updateViewPager()
                 }
             }
         }
+    }
 
     private fun tryExportEvents() {
         if (hasReadStoragePermission()) {