AP_Arming: default throttle pre-arm check to enabled

libraries/AP_Arming/AP_Arming.cpp

@@ -545,7 +545,7 @@ bool AP_Arming::rc_arm_checks(AP_Arming::Method method)
         return true;
     }
 
-    // only check if we've recieved some form of input within the last second
+    // only check if we've received some form of input within the last second
     // this is a protection against a vehicle having never enabled an input
     uint32_t last_input_ms = rc().last_input_ms();
     if ((last_input_ms == 0) || ((AP_HAL::millis() - last_input_ms) > 1000)) {
@@ -577,6 +577,7 @@ bool AP_Arming::rc_arm_checks(AP_Arming::Method method)
             }
         }
 
+        // if throttle check is enabled, require zero input
         if (rc().arming_check_throttle()) {
             RC_Channel *c = rc().channel(rcmap->throttle() - 1);
             if (c != nullptr) {