ensure that UnixDomainSocket::RecvMsgWithFlags doesn't memcpy from 0

base/posix/unix_domain_socket_linux.cc

Index: base/posix/unix_domain_socket_linux.cc
diff --git a/base/posix/unix_domain_socket_linux.cc b/base/posix/unix_domain_socket_linux.cc
index 757db983cd09dcf7d6cd293fe5d668927d619db4..436c337adb4f4e151666be2ac7d86d03458ae97a 100644
--- a/base/posix/unix_domain_socket_linux.cc
+++ b/base/posix/unix_domain_socket_linux.cc
@@ -106,8 +106,10 @@ ssize_t UnixDomainSocket::RecvMsgWithFlags(int fd,
     return -1;
   }
 
-  fds->resize(wire_fds_len);
-  memcpy(vector_as_array(fds), wire_fds, sizeof(int) * wire_fds_len);
+  if (wire_fds) {
+    fds->resize(wire_fds_len);
+    memcpy(vector_as_array(fds), wire_fds, sizeof(int) * wire_fds_len);
+  }
 
   return r;
 }