Fix use of std::array<T,1> as properties

GaudiKernel/include/GaudiKernel/ToStream.h

@@ -239,7 +239,11 @@ namespace Gaudi {
      */
     template <class TYPE, unsigned int N>
     std::ostream& toStream( const TYPE ( &obj )[N], std::ostream& s ) {
-      return toStream( obj, obj + N, s, "( ", " )", " , " );
+      if constexpr ( N == 1 ) {
+        return toStream( obj[0], s << "( " ) << " , )";
+      } else {
+        return toStream( obj, obj + N, s, "( ", " )", " , " );
+      }
     }
     // ========================================================================
     /** the specialization for std::array, a'la python tuple
@@ -248,7 +252,11 @@ namespace Gaudi {
      */
     template <class TYPE, std::size_t N>
     std::ostream& toStream( const std::array<TYPE, N>& obj, std::ostream& s ) {
-      return toStream( begin( obj ), end( obj ), s, "( ", " )", " , " );
+      if constexpr ( N == 1 ) {
+        return toStream( obj[0], s << "( " ) << " , )";
+      } else {
+        return toStream( begin( obj ), end( obj ), s, "( ", " )", " , " );
+      }
     }
     // ========================================================================
     /** the specialization for C-string, a'la python tuple