Fix select engine buffer having wrong vertex size

The theme used was wrong and the vertex size is twice as set in the theme.

source/blender/draw/engines/select/select_engine.c

@@ -193,7 +193,7 @@ static void select_cache_init(void *vedata)
     if (e_data.context.select_mode & SCE_SELECT_VERTEX) {
       DRW_PASS_CREATE(psl->select_id_vert_pass, state);
       pd->shgrp_vert = DRW_shgroup_create(sh->select_id_flat, psl->select_id_vert_pass);
-      DRW_shgroup_uniform_float_copy(pd->shgrp_vert, "sizeVertex", G_draw.block.sizeVertex);
+      DRW_shgroup_uniform_float_copy(pd->shgrp_vert, "sizeVertex", 2 * G_draw.block.sizeVertex);
     }
   }
 

source/blender/draw/intern/draw_manager.c

@@ -2682,6 +2682,7 @@ void DRW_draw_select_id(Depsgraph *depsgraph, ARegion *region, View3D *v3d, cons
   drw_viewport_var_init();
 
   /* Update UBO's */
+  UI_SetTheme(SPACE_VIEW3D, RGN_TYPE_WINDOW);
   DRW_globals_update();
 
   /* Init Select Engine */