[PATCH] [analyzer][Bugfix] RegionStore: use pointee type to create one-element regions

[Aleksei Sidorin]

I met this issue while debugging so it will take time to write a test case. But you can see that `GetElementZeroRegion()` expects //element// type but //pointer// type is returned if `Type.isNull() == true` branch. I'll provide a test case later.

http://reviews.llvm.org/D4974