Fix bootloop caused by null mIpClient in ClientModeImpl

Check if mIpClient is null before every access of this member variable.

Bug: 123990895
Test: frameworks/opt/net/wifi/tests/wifitests/runtests.sh
Test: manually test that device does not bootloop.
Change-Id: I5f173981484cc8b47053152a1c5409f167979e29
1 file changed