Fix NewLocalRef, NewGlobalRef to handle cleared weak globals.

We were not checking for null after decoding the reference, this
meant that we incorrectly created null weak global references instead
of returning null.

Issue: 63929
Change-Id: I9159682e6edad8f415ef8144fc13b9aedd2cceb4
4-byte align 64-bit values in Get/Set Double/Long for GCC 4.8.

Bug: 10837416
Change-Id: Ibb562407d81c2085666ae8824e7570f22e56eaa7
Update