[NPUW] Fix LazyTensor import (#29192)

Author: smirnov-alexey

src/plugins/intel_npu/src/plugin/npuw/compiled_model.cpp

@@ -632,7 +632,7 @@ void ov::npuw::CompiledModel::CompiledModelDesc::deserialize(std::istream& strea
 
         // Also read weights into LazyTensors
         for (std::size_t cidx = 0; cidx < closure.size(); ++cidx) {
-            if (closure_uid[cidx] != -1) {  // previously registered before serialization
+            if (closure_uid[cidx] != -1 && lazy_closure[cidx]) {  // previously registered before serialization
                 lazy_closure[cidx].read_weight(weights);
             }
         }

src/plugins/intel_npu/src/plugin/npuw/lazy_tensor.cpp

@@ -175,7 +175,9 @@ struct Unpack {
     }
     void read_weight(const ov::npuw::s11n::Weights& weights) {
         w.read_weight(weights);
-        z.read_weight(weights);
+        if (z) {  // could be empty
+            z.read_weight(weights);
+        }
         s.read_weight(weights);
     }
     void detach() {
@@ -472,6 +474,10 @@ void LazyTensor::read_weight(const ov::npuw::s11n::Weights& weights) {
     m_impl->read_weight(weights);
 }
 
+LazyTensor::operator bool() const {
+    return m_impl != nullptr;
+}
+
 std::size_t LazyTensor::get_hash() const {
     if (!m_impl) {
         return 0;

src/plugins/intel_npu/src/plugin/npuw/lazy_tensor.hpp

@@ -48,6 +48,7 @@ class LazyTensor {
     void serialize(std::ostream& stream) const;
     static LazyTensor deserialize(std::istream& stream);
     void read_weight(const ov::npuw::s11n::Weights& weights);
+    operator bool() const;
 
 private:
     std::shared_ptr<LazyTensorImpl> m_impl = nullptr;