Make sure this still works in other apps.

Signed-off-by: Marin Treselj <marin@pixelipo.com>

core/css/header.scss

@@ -137,18 +137,18 @@
 		vertical-align: middle;
 	}
 
-	.header-left,
-	.header-right {
+	#header-left, .header-left,
+	#header-right, .header-right {
 		display: inline-flex;
 		align-items: center;
 	}
 
-	.header-left {
+	#header-left, .header-left {
 		flex: 0 0;
 		flex-grow: 1;
 	}
 
-	.header-right {
+	#header-right, .header-right {
 		justify-content: flex-end;
 	}
 }