stream: fix GAP check

Gap check would consider a GAP when the current data was in fact
exactly not a gap, but next segment(s) were already available.

(cherry picked from commit 100d821a9f)

src/stream-tcp-reassemble.c

@@ -930,7 +930,7 @@ static inline bool GapAhead(TcpStream *stream, StreamingBufferBlock *cur_blk)
 {
     StreamingBufferBlock *nblk = SBB_RB_NEXT(cur_blk);
     if (nblk && (cur_blk->offset + cur_blk->len < nblk->offset) &&
-            GetAbsLastAck(stream) >= (cur_blk->offset + cur_blk->len)) {
+            GetAbsLastAck(stream) > (cur_blk->offset + cur_blk->len)) {
         return true;
     }
     return false;