[NPU] Return false in case backend is not available (#24322)

### Details:
- *Return false in case the backend is not available when using offline
compilation without having a backend*

### Tickets:
 - *ticket-id*

src/plugins/intel_npu/src/plugin/src/backends.cpp

@@ -160,7 +160,7 @@ bool NPUBackends::isBatchingSupported() const {
         return _backend->isBatchingSupported();
     }
 
-    OPENVINO_THROW("No available backend");
+    return false;
 }
 
 std::shared_ptr<IDevice> NPUBackends::getDevice(const std::string& specificName) const {