Guard synchronizedList's iteration

It's needed to guard a synchronizedList when iterating it

app/src/main/java/com/topjohnwu/magisk/ui/flash/FlashViewModel.kt

@@ -103,11 +103,13 @@ class FlashViewModel : BaseViewModel() {
             val name = "magisk_install_log_%s.log".format(now.toTime(timeFormatStandard))
             val file = MediaStoreUtils.getFile(name, true)
             file.uri.outputStream().bufferedWriter().use { writer ->
+                synchronized(logItems) {
                     logItems.forEach {
                         writer.write(it)
                         writer.newLine()
                     }
                 }
+            }
             SnackbarEvent(file.toString()).publish()
         }
     }