Fix out-of-bound memory access in loop filter
Fix out-of-bound memory access in loop filter

This commit fixes an out-of-bound memory access case in the
loop filter mask setting. This issue was introduced in

10232ed Refactor loopfilter level arrays to 2D.
https://chromium-review.googlesource.com/#/c/336645/

Change-Id: I7101a4a79b9ecfdd8ec5ef13a0b314cc95f48d12

mbebenita/aom,mbebenita/aom,luctrudeau/aom,mbebenita/aom,GrokImageCompression/aom,luctrudeau/aom,GrokImageCompression/aom,mbebenita/aom,GrokImageCompression/aom,luctrudeau/aom,mbebenita/aom,smarter/aom,luctrudeau/aom,GrokImageCompression/aom,GrokImageCompression/aom,smarter/aom,smarter/aom,smarter/aom,smarter/aom,mbebenita/aom,smarter/aom,luctrudeau/aom,mbebenita/aom,mbebenita/aom,luctrudeau/aom,mbebenita/aom,GrokImageCompression/aom