delayWorker: stop loop for static modules with no exec command

[martuscellifaria]

Hi! I am kind of new here.
I was customizing my Waybar for a couple of days and noticed a strange CPU usage spike when I add a custom separator to my config.jsonc file with interval set to 0:
"custom/sep": { "format": "|", "interval": 0 }.
This was the usage of the current v0.15.0:
ps aux | grep waybar | grep -v grep
alex 1938 0.0 0.0 8516 3388 tty2 S+ 06:40 0:00 /bin/sh -c waybar & swaync & hypridle & hyprpaper
alex 77380 11.6 0.1 788096 60124 pts/11 Sl+ 09:24 0:01 ./build/waybar
The usage spike was similar in two machines I have. Namely an ArmSoM Sige7 Pro Max and a Lenovo Ideapad Z400 Touch, both running Arch Linux, so Arm/x86 have the same behavior.

I then tracked the commits down, between v0.14.0 and v.0.15.0 and found out that commit 2b552f7 (2b552f7f) produced a side effect on setting interval = 0. Instead of the earlier behavior where interval 0 was treated as "don't start a worker", since interval_.count() == 0 skipped delayWorker() entirely, commit 2b552f7 forces a minimum of 1ms, which makes delayWorker() start and call dp.emit() in a continuous loop — even for modules with no exec command.

To have both of the new behavior of correcting sub-ms accidents and the "don't update when 0", I added the following check, so the delayWorker() function returns early if there is nothing to execute.:
if (!config_["exec"].isString() && !config_["exec-if"].isString()) { dp.emit(); return; }