Verify that there's actually a vehicle for /v respawn

Author: RussellLVP

data/messages.json

@@ -549,6 +549,7 @@
   "VEHICLE_QUICK_COLLECTABLES": "@error Keep tagging Spray Tags and shooting Red Barrels to enable this command!",
   "VEHICLE_RESET": "@success The vehicle layout has been reset.",
   "VEHICLE_RESPAWNED": "@success The %s has been respawned.",
+  "VEHICLE_RESPAWN_NOT_IN_VEHICLE": "@error %s is not in a vehicle, which can thus not be respawned.",
   "VEHICLE_SAVE_TOO_BUSY": "@error Sorry, this area is too busy! There already are %d vehicles (max: %d) and %d models (max: %d).",
   "VEHICLE_SAVED": "@success The %s has been %s in the database.",
   "VEHICLE_SEIZE_DRIVER": "@error %s is already driving your vehicle!",

javascript/features/vehicles/vehicle_commands.js

@@ -379,6 +379,10 @@ class VehicleCommands {
     // wish to reset the vehicle's position to its original spot.
     onVehicleRespawnCommand(player, subject) {
         const vehicle = subject.vehicle;
+        if (!vehicle) {
+            player.sendMessage(Message.VEHICLE_RESPAWN_NOT_IN_VEHICLE, subject.name);
+            return;
+        }
 
         // Bail out if the |subject| is not driving a vehicle, or it's not managed by this system.
         if (!this.manager_.isManagedVehicle(vehicle)) {