Fix another value is never read warning

Author: nyalldawson

src/intern/dwgutil.cpp

@@ -174,8 +174,6 @@ void dwgCompressor::decompress18(duint8 *cbuf, duint8 *dbuf, duint32 csize, duin
             compOffset = twoByteOffset(&litCount);
             if (litCount == 0)
                 litCount= litLength18();
-            else
-                oc = 0x00;
         } else if (oc > 0x20 && oc< 0x40){
             compBytes = oc - 0x1E;
             compOffset = twoByteOffset(&litCount);