Merge branch 'rm-follow-4119' into 'master'

Fix SourceID-based selection for empty input (follow !4119)

See merge request !4141

Hlt/HltDAQ/src/component/SelectViewForHltSourceID.cpp

@@ -18,8 +18,8 @@
 namespace LHCb {
 
   class SelectViewForHltSourceID : public Algorithm::Transformer<RawBank::View( RawBank::View const& )> {
-    Gaudi::Property<LHCb::Hlt::DAQ::SourceID> m_source_id{this, "SourceID", LHCb::Hlt::DAQ::SourceID::Hlt1};
-    mutable Gaudi::Accumulators::Counter<>    m_selected_banks{this, "Number of selected banks"};
+    Gaudi::Property<LHCb::Hlt::DAQ::SourceID>      m_source_id{this, "SourceID", LHCb::Hlt::DAQ::SourceID::Hlt1};
+    mutable Gaudi::Accumulators::BinomialCounter<> m_selected_banks{this, "Number of selected banks"};
 
   public:
     SelectViewForHltSourceID( const std::string& name, ISvcLocator* locator )
@@ -36,7 +36,7 @@ namespace LHCb {
         }
       }
       m_selected_banks += count;
-      auto selection = input_view.subspan( offset, count );
+      auto selection = ( offset >= 0 ) ? input_view.subspan( offset, count ) : RawBank::View{};
       return selection;
     }
   };