Changed FluxDecoder to allow zero flux reversals

Previously we'd assert in the debug version and crash in the
release version due to invalid use of the flux iterator.

Thanks to Philippe for reporting an image revealing this.

src/FluxDecoder.cpp

@@ -13,7 +13,6 @@ FluxDecoder::FluxDecoder (const FluxData &flux_revs, int bitcell_ns, int flux_sc
 	m_pll_adjust(pll_adjust)
 {
 	assert(flux_revs.size());
-	assert(flux_revs[0].size());
 
 	m_rev_it = m_flux_revs.cbegin();
 	m_flux_it = (*m_rev_it).cbegin();
@@ -111,6 +110,8 @@ int FluxDecoder::next_flux ()
 
 		m_index = true;
 		m_flux_it = (*m_rev_it).cbegin();
+		if (m_flux_it == (*m_rev_it).cend())
+			return -1;
 	}
 
 	auto time_ns = *m_flux_it++;

src/Sector.cpp

@@ -82,7 +82,7 @@ Sector::Merge Sector::add (Data &&new_data, bool bad_crc, uint8_t new_dam)
 		CRC16 crc;
 		if (encoding == Encoding::MFM) crc.init(CRC16::A1A1A1);
 		crc.add(new_dam);
-		auto bad_data_crc = crc.add(new_data.new_data(), size() + 2) != 0;
+		auto bad_data_crc = crc.add(new_data.data(), size() + 2) != 0;
 		assert(bad_crc == bad_data_crc);
 	}
 #endif