Initialize weather in tests

The tests never initialized the state of the weather system, leaving
some uninitialized values which could lead to winds in the billions of
miles per hour.  That in turn led to overflows and UB.

Initialize the weather system appropriately.

tests/test_main.cpp

@@ -146,6 +146,8 @@ static void init_global_game_state( const std::vector<mod_id> &mods,
     overmap_buffer.create_custom_overmap( point_zero, empty_specials );
 
     g->m.load( tripoint( g->get_levx(), g->get_levy(), g->get_levz() ), false );
+
+    g->weather.update_weather();
 }
 
 // Checks if any of the flags are in container, removes them all