am b84975e4: wpa_supplicant: check if ca_cert is null.

Merge commit 'b84975e4867f61e0c539cd2d782991900080e95a' into eclair-plus-aosp

* commit 'b84975e4867f61e0c539cd2d782991900080e95a':
  wpa_supplicant: check if ca_cert is null.