add lock to storage.write

lib/wallet.py

@@ -139,6 +139,9 @@ class WalletStorage(PrintError):
                 self.data.pop(key)
 
     def write(self):
+        with self.lock: self._write()
+
+    def _write(self):
         if threading.currentThread().isDaemon():
             self.print_error('warning: daemon thread cannot write wallet')
             return