fix safe acc in the general case of layer norm (#19806)

diff --git a/src/operator/nn/layer_norm-inl.h b/src/operator/nn/layer_norm-inl.h
index b440e3d..2c309ff 100644
--- a/src/operator/nn/layer_norm-inl.h
+++ b/src/operator/nn/layer_norm-inl.h
@@ -124,7 +124,7 @@
   // Calculate mean
   MSHADOW_REAL_TYPE_SWITCH(outputs[0].type_flag_, DType, {
     BROADCAST_NDIM_SWITCH(red_dst_shape.ndim(), NDim, {
-      if (safe_acc) {
+      if (!safe_acc) {
         broadcast::Reduce<mshadow_op::sum, NDim, DType, mshadow_op::identity, false>(
           s, mean_data, req[0], workspace, in_data);
       } else {
@@ -149,7 +149,7 @@
   const TBlob centered_out = outputs[0].reshape(red_src_shape);
   MSHADOW_REAL_TYPE_SWITCH(outputs[0].type_flag_, DType, {
     BROADCAST_NDIM_SWITCH(red_dst_shape.ndim(), NDim, {
-      if (safe_acc) {
+      if (!safe_acc) {
         broadcast::Reduce<mshadow_op::sum, NDim, DType, mshadow_op::square, false>(
           s, std_data, req[0], workspace, centered_out);
       } else {
@@ -290,7 +290,7 @@
   if (req[2] != kNullOp) {
     MSHADOW_REAL_TYPE_SWITCH(outputs[2].type_flag_, DType, {
       BROADCAST_NDIM_SWITCH(red_exclude_dst_shape.ndim(), NDim, {
-        if (safe_acc) {
+        if (!safe_acc) {
           broadcast::Reduce<mshadow_op::sum, NDim, DType, mshadow_op::identity, false>(
             s, outputs[2].reshape(red_exclude_dst_shape), req[2], workspace,
             ograd.reshape(red_exclude_src_shape));
@@ -313,7 +313,7 @@
   if (req[1] != kNullOp) {
     MSHADOW_REAL_TYPE_SWITCH(outputs[1].type_flag_, DType, {
       BROADCAST_NDIM_SWITCH(red_exclude_dst_shape.ndim(), NDim, {
-        if (safe_acc) {
+        if (!safe_acc) {
           broadcast::Reduce<mshadow_op::sum, NDim, DType, mshadow_op::identity, false>(
             s, outputs[1].reshape(red_exclude_dst_shape), req[1], workspace,
             ograd_mult.reshape(red_exclude_src_shape));
@@ -347,7 +347,7 @@
 #endif  // !defined(__CUDACC__)
     MSHADOW_REAL_TYPE_SWITCH(outputs[0].type_flag_, DType, {
       BROADCAST_NDIM_SWITCH(red_dst_shape.ndim(), NDim, {
-        if (safe_acc) {
+        if (!safe_acc) {
           broadcast::Reduce<mshadow_op::sum, NDim, DType, mshadow_op::identity, false>(
             s, red_out.reshape(red_dst_shape), kWriteTo, workspace,
             ograd_mult.reshape(red_src_shape));
@@ -375,7 +375,7 @@
 #endif  // !defined(__CUDACC__)
     MSHADOW_REAL_TYPE_SWITCH(outputs[0].type_flag_, DType, {
       BROADCAST_NDIM_SWITCH(red_dst_shape.ndim(), NDim, {
-        if (safe_acc) {
+        if (!safe_acc) {
           broadcast::Reduce<mshadow_op::sum, NDim, DType, mshadow_op::identity, false>(
             s, red_out.reshape(red_dst_shape), kWriteTo, workspace,
             ograd_mult.reshape(red_src_shape));