PR #4390 enabled millisecond intervals but changed image interval parsing so a missing interval could resolve to 1ms. That creates a hot update loop and can spike CPU and destabilize rendering in drawer/group setups (issue #4835).
Use explicit semantics: missing, null, non-numeric, or <=0 interval is treated as "once" (max sleep), while positive numeric values still support ms precision with a 1ms floor. This keeps the intended feature (sub-second polling when requested) without defaulting to busy looping.
Also align waybar-image(5) docs with runtime behavior.
Signed-off-by: Austin Horstman <khaneliman12@gmail.com>
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