fix: call block with plugin_default_context

[iberianpig]

I introduced plugin_defaults as an internal function for setting default values for fusuma plugins, but the search logic contained a bug.
fusuma-plugin-sendkey uses plugin_defaults to set the default value of device_names. ref: iberianpig/fusuma-plugin-sendkey#33

---
plugin:
executors:
 sendkey_executor:
   device_name: keyboard|Keyboard|KEYBOARD

Before the fix, the block was not evaluated when the context was a complete match, so the plugin could not get the default value.