statusline: Avoid showing only 'W' in workspace-diagnostics element

If you configure a subset of severities to show in the workspace
diagnostics statusline element you can see the 'W' (and surrounding
space) without any diagnostic indicators. This is the case by default
as it's configured to show warnings and errors only - if you have only
hints in your workspace like if you open `application.rs` in Helix for
example then you would see the 'W' and no indicators.

This change checks that any of the configured diagnostics are non-zero
and bails early if there are none.

helix-term/src/ui/statusline.rs

@@ -305,11 +305,21 @@ where
         },
     );
 
-    if hints > 0 || info > 0 || warnings > 0 || errors > 0 {
+    let sevs_to_show = &context.editor.config().statusline.workspace_diagnostics;
-        write(context, " W ".into(), None);
+
+    // Avoid showing the " W " if no diagnostic counts will be shown.
+    if !sevs_to_show.iter().any(|sev| match sev {
+        Severity::Hint => hints != 0,
+        Severity::Info => info != 0,
+        Severity::Warning => warnings != 0,
+        Severity::Error => errors != 0,
+    }) {
+        return;
     }
 
-    for sev in &context.editor.config().statusline.workspace_diagnostics {
+    write(context, " W ".into(), None);
+
+    for sev in sevs_to_show {
         match sev {
             Severity::Hint if hints > 0 => {
                 write(