Fixed bugs found by the compression tests

src/main/java/io/usethesource/vallang/io/binary/util/ByteBufferOutputStream.java

@@ -31,10 +31,20 @@ public void flush() throws IOException {
         if (closed) {
             throw new IOException("Stream closed");
         }
+
         target.flip();
         if (target.hasRemaining()) {
             target = flush(target);
+            if (!target.hasRemaining()) {
+                throw new IOException("flush implementation didn't correctly provide a new buffer to write to: " + target);
+            }
+        }
+        else {
+            // the buffer was empty, so flush was called on an already flushed stream
+            // so we'll reset the buffer to make sure we don't continue with empty buffer
+            target.clear();
         }
+        assert target.hasRemaining(): "after a flush, we should have a buffer with some room. (it was: " + target + ")";
     }
 
     @Override

src/main/java/io/usethesource/vallang/io/binary/wire/binary/BinaryWireOutputStream.java

@@ -36,7 +36,6 @@ public BinaryWireOutputStream(OutputStream stream, int stringSharingWindowSize)
         this(stream, stringSharingWindowSize, 8*1024);
     }
     public BinaryWireOutputStream(OutputStream stream, int stringSharingWindowSize, int bufferSize) throws IOException {
-        assert stringSharingWindowSize > 0;
         if (stream instanceof BufferedOutputStream || stream instanceof ByteBufferOutputStream) {
             __stream = stream;
         }