Handle IMSI null case when building WiFi configuration

NPE happens when trying to add passpoint profile without IMSI through
WiFiInstaller. Add null check to avoid NPE.

Bug: 28334237
Change-Id: I1b247d10b51137414c97c6d53dd83501b78c171b
1 file changed
tree: a45c07d91e2f4a8de73be8b05842c5f625b66933
  1. service/