Fix some bugs with rail variant and fix offset

when side nav was not present.

src/UIShell/Content.svelte

@@ -3,6 +3,7 @@
   export let id = "main-content";
 
   import { Grid, Row, Column } from "../Grid";
+  import { shouldRenderHamburgerMenu } from "./navStore";
 </script>
 
 <div
@@ -17,7 +18,9 @@
     >
       <Grid narrow noGutter>
         <Row>
-          <Column lg="{{ span: 13, offset: 3 }}">
+          <Column
+            lg="{$shouldRenderHamburgerMenu ? { span: 13, offset: 3 } : {}}"
+          >
             <slot />
           </Column>
         </Row>

src/UIShell/SideNav.svelte

@@ -55,8 +55,8 @@
   class:bx--side-nav__navigation="{true}"
   class:bx--side-nav="{true}"
   class:bx--side-nav--ux="{true}"
-  class:bx--side-nav--expanded="{isOpen}"
-  class:bx--side-nav--collapsed="{!isOpen}"
+  class:bx--side-nav--expanded="{isOpen && !rail}"
+  class:bx--side-nav--collapsed="{!isOpen && !rail}"
   class:bx--side-nav--rail="{rail}"
   {...$$restProps}
 >