cgen: fix option initialization with default struct initialization to…

… not be `none` (#20349)

vlib/v/gen/c/cgen.v

@@ -1980,7 +1980,8 @@ fn (mut g Gen) expr_with_tmp_var(expr ast.Expr, expr_typ ast.Type, ret_typ ast.T
 				// option ptr assignment simplification
 				if is_ptr_to_ptr_assign {
 					g.write('${tmp_var} = ')
-				} else if expr is ast.PrefixExpr && expr.right is ast.StructInit
+				} else if expr_typ.has_flag(.option) && expr is ast.PrefixExpr
+					&& expr.right is ast.StructInit
 					&& (expr.right as ast.StructInit).init_fields.len == 0 {
 					g.write('_option_none(&(${styp}[]) { ')
 				} else {

vlib/v/tests/option_ptr_init_empty_test.v

@@ -0,0 +1,30 @@
+pub struct Test {
+	a int = 10
+	b int = 5
+}
+
+pub struct ABC {
+	test  ?&Test
+	test2 ?Test
+}
+
+fn test_main() {
+	abc := ABC{
+		test: &Test{} // non option init
+		test2: Test{} // non option init
+	}
+
+	if ttt := abc.test {
+		assert ttt.a == 10
+		assert ttt.b == 5
+	} else {
+		assert false
+	}
+
+	if ttt := abc.test2 {
+		assert ttt.a == 10
+		assert ttt.b == 5
+	} else {
+		assert false
+	}
+}