Check for nullptr instead of JNI exception after using FindClass

When FindClass fails to find the specified class, it returns a
nullptr but does not always throw a JNI error/exception. This change
checks for nullptr instead of a JNI exception after using FindClass.

Bug: 112338190
Bug: 117498290
Test: atest CtsJvmtiRedefineClassesHostTestCases \
            CtsJvmtiTaggingHostTestCases \
            CtsJvmtiTrackingHostTestCases

Change-Id: Icde79b3812f877553dd085cfaa31f2b0969266c3
(cherry picked from commit 1cbfea0c428535b371d364d4f0aa92ece3c0f939)
Merged-In: Icde79b3812f877553dd085cfaa31f2b0969266c3
diff --git a/hostsidetests/jvmti/base/jni/tracking.cpp b/hostsidetests/jvmti/base/jni/tracking.cpp
index 0503e82..5ee6d57 100644
--- a/hostsidetests/jvmti/base/jni/tracking.cpp
+++ b/hostsidetests/jvmti/base/jni/tracking.cpp
@@ -108,7 +108,7 @@
 void register_android_jvmti_cts_JvmtiTrackingTest(jvmtiEnv* jenv, JNIEnv* env) {
   ScopedLocalRef<jclass> klass(env, FindClass(jenv, env,
           "android/jvmti/cts/JvmtiTrackingTest", nullptr));
-  if (env->ExceptionCheck()) {
+  if (klass.get() == nullptr) {
     env->ExceptionClear();
     return;
   }