[Process] Fix Process::getEnv() when setEnv() hasn't been called before

Author: asika32764

Process.php

@@ -53,7 +53,7 @@ class Process implements \IteratorAggregate
     private $hasCallback = false;
     private $commandline;
     private $cwd;
-    private $env;
+    private $env = [];
     private $input;
     private $starttime;
     private $lastOutputTime;

Tests/ProcessTest.php

@@ -1505,8 +1505,11 @@ public function testPreparedCommandWithNoValues()
 
     public function testEnvArgument()
     {
-        $env = ['FOO' => 'Foo', 'BAR' => 'Bar'];
         $cmd = '\\' === \DIRECTORY_SEPARATOR ? 'echo !FOO! !BAR! !BAZ!' : 'echo $FOO $BAR $BAZ';
+        $p = Process::fromShellCommandline($cmd);
+        $this->assertSame([], $p->getEnv());
+
+        $env = ['FOO' => 'Foo', 'BAR' => 'Bar'];
         $p = Process::fromShellCommandline($cmd, null, $env);
         $p->run(null, ['BAR' => 'baR', 'BAZ' => 'baZ']);