BeesBlockData: fix data type issues

Not sure if these cause any problems, but they are theoretically
incorrect data types.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>

src/bees-types.cc

@@ -945,9 +945,9 @@ BeesBlockData::data() const
 		BEESTOOLONG("Reading BeesBlockData " << *this);
 		Timer read_timer;
 
-		Blob rv(m_length);
+		Blob rv(size());
 		pread_or_die(m_fd, rv, m_offset);
-		THROW_CHECK2(runtime_error, rv.size(), m_length, ranged_cast<off_t>(rv.size()) == m_length);
+		THROW_CHECK2(runtime_error, rv.size(), size(), ranged_cast<off_t>(rv.size()) == size());
 		m_data = rv;
 		BEESCOUNT(block_read);
 		BEESCOUNTADD(block_bytes, rv.size());

src/bees.h

@@ -596,7 +596,7 @@ private:
 ostream & operator<<(ostream &os, const BeesHash &bh);
 
 class BeesBlockData {
-	using Blob = vector<char>;
+	using Blob = vector<uint8_t>;
 
 	mutable Fd		m_fd;
 	off_t			m_offset;