Fix deprecation issue with translator (#42216)

Author: driesvints

src/Illuminate/Translation/Translator.php

@@ -218,8 +218,8 @@ protected function makeReplacements($line, array $replace)
         $shouldReplace = [];
 
         foreach ($replace as $key => $value) {
-            $shouldReplace[':'.Str::ucfirst($key)] = Str::ucfirst($value);
-            $shouldReplace[':'.Str::upper($key)] = Str::upper($value);
+            $shouldReplace[':'.Str::ucfirst($key ?? '')] = Str::ucfirst($value ?? '');
+            $shouldReplace[':'.Str::upper($key ?? '')] = Str::upper($value ?? '');
             $shouldReplace[':'.$key] = $value;
         }
 

tests/Translation/TranslationTranslatorTest.php

@@ -203,6 +203,14 @@ public function testGetJsonForNonExistingReturnsSameKeyAndReplaces()
         $this->assertSame('foo baz', $t->get('foo :message', ['message' => 'baz']));
     }
 
+    public function testEmptyFallbacks()
+    {
+        $t = new Translator($this->getLoader(), 'en');
+        $t->getLoader()->shouldReceive('load')->once()->with('en', '*', '*')->andReturn([]);
+        $t->getLoader()->shouldReceive('load')->once()->with('en', 'foo :message', '*')->andReturn([]);
+        $this->assertSame('foo ', $t->get('foo :message', ['message' => null]));
+    }
+
     protected function getLoader()
     {
         return m::mock(Loader::class);