Merge branch 'bugfix/fix_sniffer_crash' into 'master'

Fix sniffer crash

See merge request sdk/ESP8266_RTOS_SDK!687

Author: wujiangang

components/esp8266/lib/VERSION

@@ -1,7 +1,7 @@
 gwen:
     core:       176661b
     net80211:   0f9461d
-    pp:         8ec2d94
+    pp:         957ad08
     wpa:        4e2372f
     espnow:     eeb16c6
     wps:        4e2372f