bug symfony#24759 Removes \n or space when $context/$extra are empty (kirkmadera)

This PR was squashed before being merged into the 3.3 branch (closes symfony#24759).

Discussion
----------

Removes \n or space when $context/$extra are empty

Simple log messages cause extra spaces or newlines when using the default format and $context or $extra are empty, resulting in output like this:

```
23:24:41 DEBUG     [test] debug

23:24:41 INFO      [test] info

23:24:41 NOTICE    [test] notice

23:24:41 WARNING   [test] warning

23:24:41 ERROR     [test] error

```

This makes reviewing command history difficult.

In the instance where $context or $extra is empty, it should not get appended with a space or newline.

| Q             | A
| ------------- | ---
| Branch?       | 3.3
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | none
| License       | MIT

Commits
-------

0d8edae Removes \n or space when / are empty

Author: fabpot

src/Symfony/Bridge/Monolog/Formatter/ConsoleFormatter.php

@@ -117,12 +117,20 @@ public function format(array $record)
         $levelColor = self::$levelColorMap[$record['level']];
 
         if ($this->options['multiline']) {
-            $context = $extra = "\n";
+            $separator = "\n";
         } else {
-            $context = $extra = ' ';
+            $separator = ' ';
+        }
+
+        $context = $this->dumpData($record['context']);
+        if ($context) {
+            $context = $separator.$context;
+        }
+ 
+        $extra = $this->dumpData($record['extra']);
+        if ($extra) {
+            $extra = $separator.$extra;
         }
-        $context .= $this->dumpData($record['context']);
-        $extra .= $this->dumpData($record['extra']);
 
         $formatted = strtr($this->options['format'], array(
             '%datetime%' => $record['datetime']->format($this->options['date_format']),