Modify reshape_input_for_matmul reduced prod to match ne for separate

Signed-off-by: Mateusz Mikolajczyk <mateusz.mikolajczyk@intel.com>

src/common/transformations/src/transformations/op_conversions/einsum_decomposition.cpp

@@ -422,6 +422,7 @@ ov::Output<ov::Node> reshape_input_for_matmul(const ov::Output<ov::Node>& input_
 
     // compute a product of a sub-shape for separate labels
     ov::OutputVector separate_parts;
+    auto reduce_axis_const = ov::op::v0::Constant::create(ov::element::Type_t::i64, ov::Shape{1}, {0});
     if (common_sub_shape.size() > 0 && separate_sub_shape.size() == 0) {
         // in this case new dimension corresponding to separate labels must be added
         // since MatMul operation is not possible to do without separate dimensions if the
@@ -432,17 +433,16 @@ ov::Output<ov::Node> reshape_input_for_matmul(const ov::Output<ov::Node>& input_
     } else if (separate_sub_shape.size() > 0) {
         // in this case compute a product of separate dimension sizes since they must be
         // presented with just one dimension for MatMul
-        auto reduce_axis_const = ov::op::v0::Constant::create(ov::element::Type_t::i64, ov::Shape{1}, {0});
         auto separate_shape_prod =
             std::make_shared<ov::op::v1::ReduceProd>(separate_sub_shape[0], reduce_axis_const, true);
         separate_parts.push_back(separate_shape_prod->output(0));
         subgraph_nodes.insert(subgraph_nodes.end(), {reduce_axis_const, separate_shape_prod});
     }
     ov::OutputVector reduced_sub_shape_prod;
     auto const_0 = ov::op::v0::Constant::create(ov::element::i32, {1}, {0});
-    for (auto sub_shape : reduced_sub_shape) {
-        auto product = std::make_shared<ov::op::v1::ReduceProd>(sub_shape, const_0, true);
-        subgraph_nodes.insert(subgraph_nodes.end(), {const_0, product});
+    if (reduced_sub_shape.size() > 0) {
+        auto product = std::make_shared<ov::op::v1::ReduceProd>(reduced_sub_shape[0], const_0, true);
+        subgraph_nodes.insert(subgraph_nodes.end(), {reduce_axis_const, product});
         reduced_sub_shape_prod.push_back(product->output(0));
     }