Fix compiler warning when dual_filter is not enabled
Fix compiler warning when dual_filter is not enabled

Change-Id: I14cd3f531af4ef0ac03deb1a19808ed1199f388f

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom