Fix version in CRH output if git describe fails

This attempts to fix the Travis-CI build after the previous commit
(efccd10) which didn't correctly handle
the fact that Travis-CI is often unable to extract the Git version.

source/resolve_hits/read_and_process_hits/hits_processor/write_results_hits_processor.cpp

@@ -33,6 +33,7 @@
 
 using namespace cath::common;
 using namespace cath::rslv::detail;
+using namespace std::literals::string_literals;
 
 using boost::algorithm::join;
 using std::move;
@@ -61,10 +62,14 @@ void write_results_hits_processor::do_process_hits_for_query(const string
 		arg_calc_hits.get_full_hits()
 	);
 
+	const string CATH_TOOLS_VERSION{ CATH_TOOLS_GIT_VERSION };
+
 	for (const ostream_ref &ostream_ref : get_ostreams() ) {
 		if ( ! written_header && ! result_full_hits.empty() ) {
 			ostream_ref.get()
-				<< "# Generated by cath-resolve-hits " << CATH_TOOLS_GIT_VERSION << ", one of the cath-tools (https://github.com/UCLOrengoGroup/cath-tools)\n";
+				<< "# Generated by cath-resolve-hits"
+				<< ( CATH_TOOLS_VERSION.empty() ? ""s : ( " " + CATH_TOOLS_VERSION ) )
+				<< ", one of the cath-tools (https://github.com/UCLOrengoGroup/cath-tools)\n";
 			ostream_ref.get()
 				<< "#FIELDS "
 				<< join(