Add test covering Uuid::fromString() being called with empty string

tests/UuidTest.php

@@ -124,6 +124,14 @@ class UuidTest extends TestCase
         $this->assertSame('ff6f8cb0-c57d-11e1-9b21-0800200c9a66', $uuid->toString());
     }
 
+    public function testFromStringWithEmptyString(): void
+    {
+        $this->expectException(InvalidUuidStringException::class);
+        $this->expectExceptionMessage('Invalid UUID string: ');
+
+        Uuid::fromString('');
+    }
+
     public function testGetBytes(): void
     {
         $uuid = Uuid::fromString('ff6f8cb0-c57d-11e1-9b21-0800200c9a66');