Copter: allow switching to throw without position estimate

The vehicle arming check will still stop the user from arming in throw mode without a good position estimate.

ArduCopter/control_throw.cpp

@@ -17,11 +17,7 @@ bool Copter::throw_init(bool ignore_checks)
     }
 
     // this mode needs a position reference
-    if (position_ok()) {
-        return true;
-    } else {
-        return false;
-    }
+    return true;
 }
 
 // clean up when exiting throw mode