Check for null pointers in oemcrypto adapter

Merge from Widevine repo of http://go/wvgerrit/100963

Test: unit tests on taimen
Bug: 156967805
Change-Id: Ic8ba7461ffcaa371a5239dca84e8a3007b0df517

libwvdrmengine/cdm/core/src/oemcrypto_adapter_dynamic.cpp

@@ -754,6 +754,10 @@ class Adapter {
     LOOKUP_ALL(8, Initialize, OEMCrypto_Initialize);
     LOOKUP_ALL(8, APIVersion, OEMCrypto_APIVersion);
     LOOKUP_ALL(8, Terminate, OEMCrypto_Terminate);
+    if (level1_.Initialize == nullptr || level1_.APIVersion == nullptr ||
+        level1_.Terminate == nullptr) {
+      level1_valid_ = false;
+    }
     if (!level1_valid_) {
       metrics->OemCryptoDynamicAdapterMetrics::SetInitializationMode(
           wvcdm::metrics::OEMCrypto_INITIALIZED_USING_L3_INVALID_L1);