Remove redundant check in gz_look().

gzread.c

@@ -157,11 +157,9 @@ local int gz_look(state)
        the output buffer is larger than the input buffer, which also assures
        space for gzungetc() */
     state->x.next = state->out;
-    if (strm->avail_in) {
     memcpy(state->x.next, strm->next_in, strm->avail_in);
     state->x.have = strm->avail_in;
     strm->avail_in = 0;
-    }
     state->how = COPY;
     state->direct = 1;
     return 0;