systemverilog-plugin: fix unnamed packed array

Signed-off-by: Kamil Rakoczy <krakoczy@antmicro.com>

systemverilog-plugin/UhdmAst.cc

diff --git a/systemverilog-plugin/UhdmAst.cc b/systemverilog-plugin/UhdmAst.cc
index aa511b4..6b72a49 100644
--- a/systemverilog-plugin/UhdmAst.cc
+++ b/systemverilog-plugin/UhdmAst.cc
@@ -1742,6 +1742,9 @@
     visit_one_to_one({vpiElemTypespec}, obj_h, [&](AST::AstNode *node) {
         if (node && node->type == AST::AST_STRUCT) {
             auto str = current_node->str;
+            // unnamed array of named (struct) array
+            if (str.empty() && !node->str.empty())
+                str = node->str;
             node->cloneInto(current_node);
             current_node->str = str;
             delete node;