VPN: fix crash on missing CCM

Bug: 350408964
Bug: 380379231
Test: atest CtsNetTestCases:android.net.cts.Ikev2VpnTest#testStartProvisionedVpnV4ProfileSession
Flag: EXEMPT bugfix
Change-Id: I2f08fb2fba667afa34f9951ff193bcb9d12683a6
Merged-In: I2f08fb2fba667afa34f9951ff193bcb9d12683a6
(cherry picked from commit 443980d0556d6f6a44d33e583d26b91821f4c2ab)
1 file changed