Don't show back-to-workspace button if there was an error loading the current operating mode

This happens when the project couldn't be loaded.
It's interesting how this bug is an artifact of the typesystem more than anything else.

Author: Byron

apps/desktop/src/components/ChromeHeader.svelte

@@ -228,7 +228,7 @@
 			{/if}
 		</div>
 
-		{#if isNotInWorkspace}
+		{#if currentMode !== null && isNotInWorkspace}
 			<Tooltip text="Switch back to gitbutler/workspace">
 				<Button
 					kind="outline"