fix(main): ignore a LoaderEntryDefault that matches no entry

When LoaderEntryDefault was set, every entry that didn't match it was
unmarked as the default, including the one set by default-entry. If the
variable named an entry that no longer exists, such as a removed kernel,
the configured default was lost and the first entry booted instead.
Only apply the variable when some entry matches it.

crates/boot/src/main.rs

@@ -325,6 +325,10 @@ fn run() -> Result<()> {
 
     // Apply bootloader interface default entry settings.
     if let Some(ref bootloader_interface_default_entry) = bootloader_interface_default_entry {
+        if entries
+            .iter()
+            .any(|entry| entry.is_match(bootloader_interface_default_entry))
+        {
             // Iterate over all the entries and mark the default entry as the one specified.
             for entry in &mut entries {
                 // Mark the entry as the default entry if it matches the specified entry.
@@ -335,6 +339,14 @@ fn run() -> Result<()> {
                     entry.unmark_default();
                 }
             }
+        } else {
+            // If no entry matches, such as when the entry was removed, the setting is ignored
+            // so that the configured default entry is still used.
+            warn!(
+                "ignoring bootloader interface default entry '{}': no matching entry",
+                bootloader_interface_default_entry
+            );
+        }
     }
 
     // Apply bootloader interface oneshot entry settings.