Throw a helpful exception if a referenced blueprint does not exist

src/Exceptions/BlueprintNotFoundException.php

@@ -0,0 +1,50 @@
+<?php
+
+namespace Statamic\Exceptions;
+
+use Exception;
+use Facade\Ignition\Support\StringComparator;
+use Facade\IgnitionContracts\BaseSolution;
+use Facade\IgnitionContracts\ProvidesSolution;
+use Facade\IgnitionContracts\Solution;
+use Statamic\Facades\Blueprint;
+use Statamic\Statamic;
+
+class BlueprintNotFoundException extends Exception implements ProvidesSolution
+{
+    protected $blueprintHandle;
+    protected $namespace;
+
+    public function __construct($blueprintHandle, $namespace = null)
+    {
+        parent::__construct("Blueprint [{$blueprintHandle}] not found");
+
+        $this->blueprintHandle = $blueprintHandle;
+        $this->namespace = $namespace;
+    }
+
+    public function getSolution(): Solution
+    {
+        $description = ($suggestedBlueprint = $this->getSuggestedBlueprint())
+            ? "Did you mean `$suggestedBlueprint`?"
+            : 'Are you sure the blueprint exists?';
+
+        return BaseSolution::create("The {$this->blueprintHandle} blueprint was not found.")
+            ->setSolutionDescription($description)
+            ->setDocumentationLinks([
+                'Read the blueprints guide' => Statamic::docsUrl('/blueprints'),
+            ]);
+    }
+
+    protected function getSuggestedBlueprint()
+    {
+        if (! $this->namespace) {
+            return null;
+        }
+
+        return StringComparator::findClosestMatch(
+            Blueprint::in($this->namespace)->map->handle()->values()->all(),
+            $this->blueprintHandle
+        );
+    }
+}

src/Http/Controllers/CP/Collections/EntriesController.php

@@ -6,6 +6,7 @@
 use Illuminate\Validation\ValidationException;
 use Statamic\Contracts\Entries\Entry as EntryContract;
 use Statamic\CP\Breadcrumbs;
+use Statamic\Exceptions\BlueprintNotFoundException;
 use Statamic\Facades\Asset;
 use Statamic\Facades\Entry;
 use Statamic\Facades\Site;
@@ -76,6 +77,10 @@ public function edit(Request $request, $collection, $entry)
 
         $blueprint = $entry->blueprint();
 
+        if (! $blueprint) {
+            throw new BlueprintNotFoundException($entry->value('blueprint'), 'collections/'.$collection->handle());
+        }
+
         if (User::current()->cant('edit-other-authors-entries', [EntryContract::class, $collection, $blueprint])) {
             $blueprint->ensureFieldHasConfig('author', ['read_only' => true]);
         }