chore(io): rewrite certain error messages

We can do this now that we know that it won't be because of any
unimplemented feature in some circumstances

src/util.zig

@@ -143,7 +143,7 @@ pub const io = struct {
             return 0;
         }
 
-        pub fn undef(comptime T: type, log: anytype, comptime format: []const u8, args: anytype) ?T {
+        pub fn undef(comptime T: type, comptime log: anytype, comptime format: []const u8, args: anytype) ?T {
             @setCold(true);
 
             const unhandled_io = config.config().debug.unhandled_io;
@@ -153,6 +153,13 @@ pub const io = struct {
 
             return null;
         }
+
+        pub fn err(comptime T: type, comptime log: anytype, comptime format: []const u8, args: anytype) ?T {
+            @setCold(true);
+
+            log.err(format, args);
+            return null;
+        }
     };
 
     pub const write = struct {