fix(708): Handle null timing pointer in CEA-708 settings conversion

When converting CEA-708 decoder settings from C to Rust via from_ctype(),
a null timing pointer would cause the entire conversion to fail and return
None. This triggered the unwrap_or(default()) fallback, resetting critical
settings like `enabled` and `services_enabled` to false/0.

This caused CEA-708 captions to not be extracted (exit code 10) even when
--service was specified, because the decoder's is_active flag was reset
to 0 during demuxer initialization.

The fix handles null timing pointer gracefully by using a default
CommonTimingCtx instead of propagating None, preserving the other
decoder settings.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: cfsmp3

src/rust/src/ctorust.rs

@@ -121,19 +121,25 @@ impl FromCType<ccx_decoder_dtvcc_settings> for DecoderDtvccSettings {
         {
             services_enabled[i] = flag != 0;
         }
+        // Handle timing - use default if pointer is null to avoid losing other settings
+        let timing = if settings.timing.is_null() {
+            CommonTimingCtx::default()
+        } else {
+            CommonTimingCtx::from_ctype(settings.timing).unwrap_or_default()
+        };
 
         Some(DecoderDtvccSettings {
             enabled: settings.enabled != 0,
             print_file_reports: settings.print_file_reports != 0,
             no_rollup: settings.no_rollup != 0,
             report: if !settings.report.is_null() {
-                Some(DecoderDtvccReport::from_ctype(settings.report)?)
+                DecoderDtvccReport::from_ctype(settings.report)
             } else {
                 None
             },
             active_services_count: settings.active_services_count,
             services_enabled,
-            timing: CommonTimingCtx::from_ctype(settings.timing)?,
+            timing,
         })
     }
 }