fix(mgb/opr-mm): fix m_megray_ctx init

GitOrigin-RevId: 7804fbe2ef28b6014e3f82a59675948442665e7d

src/opr-mm/impl/collective_comm.cpp

@@ -408,7 +408,6 @@ CollectiveComm::CollectiveComm(
             "CollectiveComm inputs should not contain duplicated input device");
 
     ModeTrait::from_mode(param.mode).add_output_var(this, inp_cn);
-    m_megray_ctx = MegRay::CudaContext::make(get_stream(output(0)));
 
     const char* c_debug = MGB_GETENV("MGE_MM_OPR_DEBUG");
     if (c_debug != nullptr and strcmp(c_debug, "1") == 0) {
@@ -469,6 +468,8 @@ void CollectiveComm::opr_register() {
             hash, m_key, m_nr_devices, m_rank,
             get_megray_backend(m_backend), m_group_client);
 
+    m_megray_ctx = MegRay::CudaContext::make(get_stream(output(0)));
+
     m_init = true;
 }