Bug fix

When the compressor recognized that a shape was a single color, it determines
an optimal encoding for that color. However, only the error in the single
pixel was returned as the error for the overall shape. This caused problems
with modes that do not support alpha and shapes that do have alpha.

BPTCEncoder/src/BC7Compressor.cpp

@@ -985,7 +985,7 @@ double BC7CompressionMode::CompressCluster(const RGBACluster &cluster, RGBAVecto
       bestIndices[i] = 1;
     }
     
-    return bestErr;
+    return cluster.GetNumPoints() * bestErr;
   }
   
   const uint32 nBuckets = (1 << GetNumberOfBitsPerIndex());