Set item variable "weight" to milligrams, because that is used in `it…

…em::weight` when the value of that variable is loaded.

src/iuse.cpp

@@ -9263,7 +9263,8 @@ int item::contain_monster( const tripoint &target )
             new_weight = 200000;
             break;
     }
-    set_var( "weight", new_weight );
+    // Above is old code. It uses gram as units for monster weight.
+    set_var( "weight", to_milligram( units::from_gram( new_weight ) ) );
     g->remove_zombie( f );
     return 0;
 }

src/units.h

@@ -342,6 +342,12 @@ inline constexpr quantity<value_type, mass_in_milligram_tag> from_kilogram(
     return from_gram( v * 1000 );
 }
 
+template<typename value_type>
+inline constexpr value_type to_milligram( const quantity<value_type, mass_in_milligram_tag> &v )
+{
+    return v.value();
+}
+
 template<typename value_type>
 inline constexpr value_type to_gram( const quantity<value_type, mass_in_milligram_tag> &v )
 {

src/vehicle_use.cpp

@@ -814,7 +814,7 @@ bool vehicle::fold_up()
     }
 
     if( can_be_folded ) {
-        bicycle.set_var( "weight", to_gram( total_mass() ) );
+        bicycle.set_var( "weight", to_milligram( total_mass() ) );
         bicycle.set_var( "volume", total_folded_volume() / units::legacy_volume_factor );
         bicycle.set_var( "name", string_format( _( "folded %s" ), name ) );
         bicycle.set_var( "vehicle_name", name );