[plugin] Exporter: ensure we're connected before sending highlights (#8604)

plugins/exporter.koplugin/main.lua

@@ -299,7 +299,8 @@ For more information, please visit https://github.com/koreader/koreader/wiki/Hig
                     return not self:isDocless() and self:readyToExport() and not self.txt_export
                 end,
                 callback = function()
-                    UIManager:scheduleIn(0.5, function()
+                    local export_callback = function()
+                        UIManager:nextTick(function()
                             self:exportCurrentNotes(self.view)
                         end)
 
@@ -308,6 +309,12 @@ For more information, please visit https://github.com/koreader/koreader/wiki/Hig
                             timeout = 1,
                         })
                     end
+                    if self.joplin_export or self.readwise_export then
+                        NetworkMgr:runWhenOnline(export_callback)
+                    else
+                        export_callback()
+                    end
+                end
             },
             {
                 text = _("Export all notes in your library"),
@@ -315,7 +322,8 @@ For more information, please visit https://github.com/koreader/koreader/wiki/Hig
                     return self:readyToExport()
                 end,
                 callback = function()
-                    UIManager:scheduleIn(0.5, function()
+                    local export_callback = function()
+                        UIManager:nextTick(function()
                             self:exportAllNotes()
                         end)
 
@@ -323,6 +331,13 @@ For more information, please visit https://github.com/koreader/koreader/wiki/Hig
                             text = _("Exporting may take several minutes…"),
                             timeout = 1,
                         })
+                    end
+                    if self.joplin_export or self.readwise_export then
+                        NetworkMgr:runWhenOnline(export_callback)
+                    else
+                        export_callback()
+                    end
+
                 end,
                 separator = true,
             },