small changes

mix/CodeModel.cpp

@@ -333,7 +333,8 @@ void CodeModel::runCompilationJob(int _jobId)
 
 void CodeModel::gasEstimation(solidity::CompilerStack const& _cs)
 {
-	m_gasCostsMaps->deleteLater();
+	if (m_gasCostsMaps)
+		m_gasCostsMaps->deleteLater();
 	m_gasCostsMaps = new GasMapWrapper(this);
 	for (std::string n: _cs.getContractNames())
 	{

mix/CodeModel.h

@@ -244,7 +244,7 @@ private:
 	mutable dev::Mutex x_contractMap;
 	ContractMap m_contractMap;
 	SourceMaps m_sourceMaps;
-	GasMapWrapper* m_gasCostsMaps;
+	GasMapWrapper* m_gasCostsMaps = 0;
 	std::unique_ptr<CodeHighlighterSettings> m_codeHighlighterSettings;
 	QThread m_backgroundThread;
 	BackgroundWorker m_backgroundWorker;