turn on -Werror and fix resulting errors

src/modules/bottle_drop/bottle_drop.cpp

@@ -523,6 +523,9 @@ BottleDrop::task_main()
 			}
 
 			switch (_drop_state) {
+				case DROP_STATE_INIT:
+					// do nothing
+					break;
 
 				case DROP_STATE_TARGET_VALID:
 				{
@@ -689,6 +692,10 @@ BottleDrop::task_main()
 						orb_publish(ORB_ID(onboard_mission), _onboard_mission_pub, &_onboard_mission);
 					}
 					break;
+
+				case DROP_STATE_BAY_CLOSED:
+					// do nothing
+					break;
 			}
 
 			counter++;