php8.3: fix deprecated passing null to str_replace() (OpenMage#4525)

* php8.3: fix passing null to `str_replace()`

* fix

Author: sreichel

lib/Varien/Object.php

@@ -589,7 +589,8 @@ public function toString($format = '')
         } else {
             preg_match_all('/\{\{([a-z0-9_]+)\}\}/is', $format, $matches);
             foreach ($matches[1] as $var) {
-                $format = str_replace('{{' . $var . '}}', $this->getData($var), $format);
+                $replace = is_null($this->getData($var)) ? '' : $this->getData($var);
+                $format = str_replace('{{' . $var . '}}', $replace, $format);
             }
             $str = $format;
         }

tests/unit/Varien/ObjectTest.php

@@ -166,15 +166,33 @@ public function provideGetDataData(): Generator
     }
 
     /**
+     * @dataProvider provideToString
      * @group Varien_Object
      */
-    public function testToString(): void
+    public function testToString(string $expectedResult, string $format): void
     {
-        $this->subject->setString1('open');
-        $this->subject->setString2('mage');
-        $this->assertSame('open, mage', $this->subject->toString());
-        $this->assertSame('openmage', $this->subject->toString('{{string1}}{{string2}}'));
-        $this->assertSame('open', $this->subject->toString('{{string1}}{{string_not_exists}}'));
+        $this->subject->setString0('0');
+        $this->subject->setString1('one');
+        $this->subject->setString2('two');
+        $this->subject->setString3('three');
+
+        $this->assertSame($expectedResult, $this->subject->toString($format));
+    }
+
+    public function provideToString(): Generator
+    {
+        yield 'no format' => [
+            '0, one, two, three',
+            '',
+        ];
+        yield 'valid' => [
+            '0 one two',
+            '{{string0}} {{string1}} {{string2}}',
+        ];
+        yield 'invalid' => [
+            'three  0',
+            '{{string3}} {{string_not_exists}} {{string0}}',
+        ];
     }
 
     /**