!12536 Fix ConvertAttrValuetoString error when attr value is null

From: @irmo
Reviewed-by: @zh_qh,@hwhewei
Signed-off-by: @zh_qh

mindspore/ccsrc/backend/optimizer/ascend/mindir/conv2d_unify_mindir.cc

@@ -223,7 +223,11 @@ void SetConv2DAttrs(const CNodePtr &conv2d, const CNodePtr &depth_conv) {
   SetCommonAttrs(conv2d, depth_conv);
   AnfAlgo::CopyNodeAttr(kAttrInputNames, conv2d, depth_conv);
   AnfAlgo::CopyNodeAttr(kAttrStride, conv2d, depth_conv);
-  AnfAlgo::CopyNodeAttr(kAttrOffsetA, conv2d, depth_conv);
+  if (AnfAlgo::HasNodeAttr(kAttrOffsetA, conv2d)) {
+    AnfAlgo::CopyNodeAttr(kAttrOffsetA, conv2d, depth_conv);
+  } else {
+    AnfAlgo::SetNodeAttr(kAttrOffsetA, MakeValue(0), depth_conv);
+  }
 }
 
 void SetConv2DBackpropInputAttrs(const CNodePtr &conv2d_backin, const CNodePtr &depth_conv_backin) {

mindspore/core/utils/check_convert_utils.cc

@@ -231,7 +231,7 @@ bool CheckAndConvertUtils::ConvertAttrValueToInt(const std::string &op_type, con
 bool CheckAndConvertUtils::ConvertAttrValueToString(const std::string &op_type, const std::string &attr_name,
                                                     ValuePtr *const value) {
   if (value == nullptr || *value == nullptr) {
-    MS_LOG(ERROR) << "value is nullptr";
+    MS_LOG(INFO) << "value is nullptr! op_type = " << op_type << ", attr_name = " << attr_name;
     return false;
   }
   if (!(*value)->isa<Int64Imm>()) {
@@ -587,7 +587,7 @@ TypeId CheckAndConvertUtils::CheckTypeSame(const std::string &arg_name, const Ty
 bool CheckAndConvertUtils::CheckIrAttrtoOpAttr(const std::string &op_type, const std::string &attr_name,
                                                ValuePtr *const value) {
   if (*value == nullptr) {
-    MS_LOG(ERROR) << "value is nullptr";
+    MS_LOG(INFO) << "value is nullptr! op_type = " << op_type << ", attr_name = " << attr_name;
     return false;
   }
   if (op_type.empty() || attr_name.empty()) {