fix(plex): replace stray NUL byte with a space in the duration sentinel

PlexSidebar.tsx carried a literal 0x00 byte in the duration-filter
FilterChipGroup's off-bucket sentinel (`... ? "" : "\0"`), where a normal space
was intended. Functionally inert (both the NUL and a space match no bucket
option, so a set-but-off-bucket duration selects nothing), but a NUL in source
is corruption — replaced with an ASCII space. No NUL bytes remain in src.

frontend/src/components/PlexSidebar.tsx

@@ -336,7 +336,7 @@ export default function PlexSidebar({ layout, setLayout, collapsed, onToggleColl
                 // duration (e.g. stale state after a bucket-boundary change) selects nothing, not "Any".
                 value={
                   durBucketKey ??
-                  (filters.durationMin == null && filters.durationMax == null ? "" : "")
+                  (filters.durationMin == null && filters.durationMax == null ? "" : " ")
                 }
                 options={[
                   { value: "", label: t("plex.filter.any") },