Fix T62438: Unhide all doesn't set newly visible objects to selected

The select option in the operator was never working because we were
trying to select an object considered unselectable (since it was hidden).

Reviewers: brecht

Differential Revision: https://developer.blender.org/D4527

source/blender/editors/object/object_edit.c

@@ -77,6 +77,7 @@
 #include "BKE_softbody.h"
 #include "BKE_editmesh.h"
 #include "BKE_report.h"
+#include "BKE_scene.h"
 #include "BKE_workspace.h"
 
 #include "DEG_depsgraph.h"
@@ -162,7 +163,10 @@ static int object_hide_view_clear_exec(bContext *C, wmOperator *op)
 			changed = true;
 
 			if (select) {
-				ED_object_base_select(base, BA_SELECT);
+				/* We cannot call `ED_object_base_select` because
+				 * base is not selectable while it is hidden. */
+				base->flag |= BASE_SELECTED;
+				BKE_scene_object_base_flag_sync_from_base(base);
 			}
 		}
 	}