First quickfix for some of the problems mentioned in issue #163.

* C backend: do not expect body->arg(0) to always exist in emit_epilogue.
* LLVM Backend: Do not expect ret to exist in CodeGen::convert(Type*).

src/thorin/be/c/c.cpp

@@ -686,7 +686,9 @@ void CCodeGen::emit_epilogue(Continuation* cont) {
     auto&& bb = cont2bb_[cont];
     assert(cont->has_body());
     auto body = cont->body();
-    emit_debug_info(bb.tail, body->arg(0));
+    if (body->num_args() > 0) {
+        emit_debug_info(bb.tail, body->arg(0));
+    }
 
     if ((lang_ == Lang::OpenCL || (lang_ == Lang::HLS && hls_top_scope)) && (cont->is_exported()))
         emit_fun_decl(cont);

src/thorin/be/llvm/llvm.cpp

@@ -160,7 +160,10 @@ llvm::Type* CodeGen::convert(const Type* type) {
                 } else
                     ops.push_back(convert(op));
             }
-            assert(ret);
+
+            if (!ret) {
+                ret = llvm::Type::getVoidTy(context());
+            }
 
             if (type->tag() == Node_FnType) {
                 auto llvm_type = llvm::FunctionType::get(ret, ops, false);