bug #20328 [Console] Fix empty COLUMNS/LINES env vars (nicolas-grekas)

This PR was merged into the 3.2-dev branch.

Discussion
----------

[Console] Fix empty COLUMNS/LINES env vars

| Q             | A
| ------------- | ---
| Branch?       | 3.2
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Here is a python app that fails otherwise:

test.py:
```python
import os

int(os.environ.get('COLUMNS', 80))
```

test.php:
```php
<?php
putenv('COLUMNS=');
passthru('python test.py');
```

result:
```
$ php test.php
Traceback (most recent call last):
 File "test.py", line 3, in <module>
   int(os.environ.get('COLUMNS', 80))
ValueError: invalid literal for int() with base 10: ''
```

Commits
-------

8ad991e [Console] Fix empty COLUMNS/LINES env vars

src/Symfony/Component/Console/Terminal.php

@@ -31,7 +31,7 @@ class Terminal
             self::initDimensions();
         }
 
-        return self::$width;
+        return self::$width ?: 80;
     }
 
     /**
@@ -49,7 +49,7 @@ class Terminal
             self::initDimensions();
         }
 
-        return self::$height;
+        return self::$height ?: 50;
     }
 
     private static function initDimensions()