Warn about invalidvalue in reduceExpr

Signed-off-by: Wojciech Sipak <wsipak@antmicro.com>

systemverilog-plugin/UhdmAst.cc

diff --git a/systemverilog-plugin/UhdmAst.cc b/systemverilog-plugin/UhdmAst.cc
index 3a2524e..e7d264e 100644
--- a/systemverilog-plugin/UhdmAst.cc
+++ b/systemverilog-plugin/UhdmAst.cc
@@ -2357,7 +2357,9 @@
     bool invalidvalue = false;
     UHDM::ExprEval eval;
     UHDM::expr *resolved_operation = eval.reduceExpr(expr, invalidvalue, inst, pexpr);
-    log_assert(!invalidvalue);
+    if (invalidvalue) {
+        log_file_warning(std::string(expr->VpiFile()), expr->VpiLineNo(), "Could not reduce expression.\n");
+    }
     return resolved_operation;
 }