Fix crashes on assignment to dummies

Author: povik

src/procedural.cc

@@ -201,6 +201,9 @@ void ProceduralContext::update_variable_state(slang::SourceLocation loc, Variabl
 					seen_nonblocking_assignment[chunk.variable] = loc;
 				}
 			}
+		} else if (chunk.variable.kind == Variable::Dummy) {
+			// Dummies are for graceful error handling and require
+			// no checking of blocking or nonblocking case
 		} else {
 			// This is expected to be an AST invariant -- we don't have a symbol
 			// to use here for the ast_invariant() helper, so it's a plain

src/slang_frontend.cc

@@ -429,7 +429,9 @@ RTLIL::SigSpec VariableState::evaluate(NetlistContext &netlist, VariableBits vbi
 {
 	RTLIL::SigSpec ret;
 	for (auto vbit : vbits) {
-		if (visible_assignments.count(vbit)) {
+		if (vbit.variable.kind == Variable::Dummy) {
+			ret.append(RTLIL::Sx);
+		} else if (visible_assignments.count(vbit)) {
 			ret.append(visible_assignments.at(vbit));
 		} else {
 			log_assert(vbit.variable.kind == Variable::Static);