fix(switch_translator): skip switches with no state labels

Fixes #866
Closes #640

Squashed commit of the following:

commit e3addcf
Author: groverlynn <groverlynn@gmail.com>
Date:   Tue Mar 28 01:07:39 2023 +0200

    Skip switches with no state labels

---------

Co-authored-by: 居戎氏 <chen.sst@gmail.com>

Author: groverlynn

src/rime/gear/switch_translator.cc

@@ -30,6 +30,11 @@ inline static string get_state_label(const SwitchOption& option,
       Switches::GetStateLabel(option.the_switch, state_index, abbreviate));
 }
 
+inline static bool has_state_label(const SwitchOption& option,
+                                   size_t state_index) {
+  return bool(Switches::GetStateLabel(option.the_switch, state_index, false));
+}
+
 class Switch : public SimpleCandidate, public SwitcherCommand {
  public:
   Switch(const SwitchOption& option, bool current_state, bool auto_save)
@@ -208,6 +213,9 @@ void SwitchTranslation::LoadSwitches(Switcher* switcher) {
   switches.FindOption(
       [this, switcher, context,
        &groups](Switches::SwitchOption option) -> Switches::FindResult {
+        if (!has_state_label(option, 0)) {
+          return Switches::kContinue;
+        }
         if (option.type == Switches::kToggleOption) {
           bool current_state = context->get_option(option.option_name);
           Append(New<Switch>(option, current_state,
@@ -234,9 +242,11 @@ void SwitchTranslation::LoadSwitches(Switcher* switcher) {
             Switches::SwitchOption option) -> Switches::FindResult {
           bool current_state = context->get_option(option.option_name);
           if (option.type == Switches::kToggleOption) {
-            folded_options->Append(option, current_state);
+            if (has_state_label(option, current_state)) {
+              folded_options->Append(option, current_state);
+            }
           } else if (option.type == Switches::kRadioGroup) {
-            if (current_state) {
+            if (current_state && has_state_label(option, option.option_index)) {
               folded_options->Append(option, option.option_index);
             }
           }

src/rime/switches.h

@@ -17,6 +17,8 @@ struct StringSlice {
   operator string() const {
     return str && length ? string(str, length) : string();
   }
+
+  operator bool() const { return bool(str) && bool(length); }
 };
 
 class Switches {