Fix 2101425: Camera crashes spontaneously in preview.

The problem is we missed an "obj" parameter while calling
postEventFromNative (which put it in a field of a Message object),
so a garbage value on stack is used.

When the GC tries to follow that "obj" field, expecting to find
another object, it crashes.
diff --git a/core/jni/android_hardware_Camera.cpp b/core/jni/android_hardware_Camera.cpp
index 6b92994..e944654 100644
--- a/core/jni/android_hardware_Camera.cpp
+++ b/core/jni/android_hardware_Camera.cpp
@@ -112,7 +112,7 @@
     }
     JNIEnv *env = AndroidRuntime::getJNIEnv();
     env->CallStaticVoidMethod(mCameraJClass, fields.post_event,
-            mCameraJObjectWeak, msgType, ext1, ext2);
+            mCameraJObjectWeak, msgType, ext1, ext2, NULL);
 }
 
 void JNICameraContext::copyAndPost(JNIEnv* env, const sp<IMemory>& dataPtr, int msgType)