checker: check undefined ident in reference selector (#14949)

vlib/v/checker/checker.v

@@ -1124,6 +1124,7 @@ pub fn (mut c Checker) selector_expr(mut node ast.SelectorExpr) ast.Type {
 		// This means that the field has an undefined type.
 		// This error was handled before.
 		// c.error('`void` type has no fields', node.pos)
+		node.expr_type = ast.void_type
 		return ast.void_type
 	}
 	node.expr_type = typ

vlib/v/checker/tests/undefined_ident_in_ref_selector.out

@@ -0,0 +1,6 @@
+vlib/v/checker/tests/undefined_ident_in_ref_selector.vv:6:10: error: undefined ident: `line`
+    4 |
+    5 | fn read() int {
+    6 |     return &line.len
+      |             ~~~~
+    7 | }

vlib/v/checker/tests/undefined_ident_in_ref_selector.vv

@@ -0,0 +1,7 @@
+module main
+
+fn main() {}
+
+fn read() int {
+	return &line.len
+}