Fix build with GCC 6.

Gentoo-bug: 594188

--- a/hupnp/src/devicehosting/devicehost/hservermodel_creator_p.cpp
+++ b/hupnp/src/devicehosting/devicehost/hservermodel_creator_p.cpp
@@ -493,7 +493,7 @@
             QString("Failed to initialize device [%1]").arg(
                 deviceInfo.udn().toString());
 
-        return false;
+        return NULL;
     }
 
     device->h_ptr->m_deviceDescription =
@@ -560,7 +560,7 @@
                     "[%2]").arg(device->info().deviceType().toString(),
                                 dt.toString());
 
-                return false;
+                return NULL;
             }
         }
     }