Fix risky test

We need to mock out the LoggerInterface's error call so that it doesn't
call error_log() behind the scenes on us as this will output a new line
character and cause a risky test notice.

Author: akrabat

tests/Handlers/ErrorHandlerTest.php

@@ -10,6 +10,7 @@
 
 namespace Slim\Tests\Handlers;
 
+use Prophecy\Argument;
 use Psr\Http\Message\ResponseInterface;
 use Psr\Log\LoggerInterface;
 use ReflectionClass;
@@ -392,7 +393,16 @@ public function testLogErrorRenderer()
             ->willReturn($renderer)
             ->shouldBeCalledOnce();
 
-        $handler = new ErrorHandler($callableResolverProphecy->reveal(), $this->getResponseFactory());
+        $loggerProphecy = $this->prophesize(LoggerInterface::class);
+        $loggerProphecy
+            ->error(Argument::type('string'))
+            ->shouldBeCalled();
+
+        $handler = new ErrorHandler(
+            $callableResolverProphecy->reveal(),
+            $this->getResponseFactory(),
+            $loggerProphecy->reveal()
+        );
         $handler->setLogErrorRenderer('logErrorRenderer');
 
         $displayErrorDetailsProperty = new ReflectionProperty($handler, 'displayErrorDetails');