Add nullptr check in PluginVC read and write (#11961)

src/proxy/PluginVC.cc

@@ -483,7 +483,7 @@ PluginVC::process_write_side()
   need_write_process = false;
 
   // Check write_state
-  if (write_state.vio.op != VIO::WRITE || closed || write_state.shutdown) {
+  if (write_state.vio.cont == nullptr || write_state.vio.op != VIO::WRITE || closed || write_state.shutdown) {
     return;
   }
 
@@ -493,9 +493,13 @@ PluginVC::process_write_side()
     return;
   }
 
-  IOBufferReader *reader      = write_state.vio.get_reader();
-  int64_t         bytes_avail = reader->read_avail();
-  int64_t         act_on      = std::min(bytes_avail, ntodo);
+  IOBufferReader *reader = write_state.vio.get_reader();
+  if (reader == nullptr) {
+    return;
+  }
+
+  int64_t bytes_avail = reader->read_avail();
+  int64_t act_on      = std::min(bytes_avail, ntodo);
 
   Dbg(dbg_ctl_pvc, "[%u] %s: process_write_side; act_on %" PRId64 "", core_obj->id, PVC_TYPE, act_on);
 
@@ -601,7 +605,8 @@ PluginVC::process_read_side()
   need_read_process = false;
 
   // Check read_state
-  if (read_state.vio.op != VIO::READ || closed || read_state.shutdown || !read_state.vio.ntodo()) {
+  if (read_state.vio.cont == nullptr || read_state.vio.op != VIO::READ || closed || read_state.shutdown ||
+      !read_state.vio.ntodo()) {
     return;
   }