Fix origin migrator for SSO logins

For some reason this was trying to close the same window twice
when the app was reloaded after an SSO login. Possibly also a
problem on electron < 6 - presumably a race condition.

electron_app/src/originMigrator.js

@@ -33,7 +33,7 @@ async function migrateFromOldOrigin() {
                 webgl: false,
             },
         });
-        ipcMain.on('origin_migration_complete', (e, success, sentSummary, storedSummary) => {
+        ipcMain.once('origin_migration_complete', (e, success, sentSummary, storedSummary) => {
             if (success) {
                 console.log("Origin migration completed successfully!");
             } else {
@@ -44,7 +44,7 @@ async function migrateFromOldOrigin() {
             migrateWindow.close();
             resolve();
         });
-        ipcMain.on('origin_migration_nodata', (e) => {
+        ipcMain.once('origin_migration_nodata', (e) => {
             console.log("No session to migrate from old origin");
             migrateWindow.close();
             resolve();