Fix Generate click going silent after adding the watchdog-arm step

Live logs showed zero server-side activity after a Generate click —
not even the CPU-preprocessing print statements that normally fire
first — meaning the request never reached the backend at all.

The newly added watchdog-arming step was the only fn=None (JS-only,
unqueued per blocks.py's `queue = False if fn is None else queue`)
dependency in this app using inputs=None; every other fn=None step
(slot visibility) uses a real inputs=[...] list and is confirmed
working. inputs=None combined with fn=None is an untested combination
and the most likely place for the chain to break before ever reaching
the real generate call. Switched to inputs=[] to match the known-good
pattern.

app.py

@@ -3163,7 +3163,7 @@ with gr.Blocks(title="Generate Audio for Video", css=_SLOT_CSS, js=_GLOBAL_JS) a
                 outputs=[taro_btn],
             ).then(
                 fn=None,
-                inputs=None,
+                inputs=[],
                 outputs=[],
                 js="() => window._armGenerateWatchdog('taro_btn', 600000)",
             ).then(
@@ -3234,7 +3234,7 @@ with gr.Blocks(title="Generate Audio for Video", css=_SLOT_CSS, js=_GLOBAL_JS) a
                 outputs=[mma_btn],
             ).then(
                 fn=None,
-                inputs=None,
+                inputs=[],
                 outputs=[],
                 js="() => window._armGenerateWatchdog('mma_btn', 600000)",
             ).then(
@@ -3304,7 +3304,7 @@ with gr.Blocks(title="Generate Audio for Video", css=_SLOT_CSS, js=_GLOBAL_JS) a
                 outputs=[hf_btn],
             ).then(
                 fn=None,
-                inputs=None,
+                inputs=[],
                 outputs=[],
                 js="() => window._armGenerateWatchdog('hf_btn', 600000)",
             ).then(