Review handling is global function detection.

Fixes !sensor been selectable in global scripts

Thanks to @Max for his help

radio/src/gui/gui_common_arm.cpp

@@ -99,7 +99,7 @@ bool isTelemetryFieldComparisonAvailable(int index)
 {
   if (!isTelemetryFieldAvailable(index))
     return false;
-    
+
   TelemetrySensor & sensor = g_model.telemetrySensors[index];
   if (sensor.unit >= UNIT_DATETIME)
     return false;
@@ -354,7 +354,10 @@ bool isSwitchAvailable(int swtch, SwitchContext context)
   }
 
   if (swtch >= SWSRC_FIRST_SENSOR && swtch <= SWSRC_LAST_SENSOR) {
-    return isTelemetryFieldAvailable(swtch - SWSRC_FIRST_SENSOR);
+    if (context == GeneralCustomFunctionsContext)
+     return false;
+    else
+      return isTelemetryFieldAvailable(swtch - SWSRC_FIRST_SENSOR);
   }
 
   return true;
@@ -701,4 +704,4 @@ void editStickHardwareSettings(coord_t x, coord_t y, int idx, event_t event, Lcd
     editName(x, y, g_eeGeneral.anaNames[idx], LEN_ANA_NAME, event, flags);
   else
     lcdDrawMMM(x, y, flags);
-}
+}