Skip empty time values

src/Composer/Repository/Vcs/GitBitbucketDriver.php

@@ -93,7 +93,7 @@ class GitBitbucketDriver extends VcsDriver implements VcsDriverInterface
 
             $composer = JsonFile::parseJson($composer, $resource);
 
-            if (!isset($composer['time'])) {
+            if (empty($composer['time'])) {
                 $resource = $this->getScheme() . '://api.bitbucket.org/1.0/repositories/'.$this->owner.'/'.$this->repository.'/changesets/'.$identifier;
                 $changeset = JsonFile::parseJson($this->getContents($resource), $resource);
                 $composer['time'] = $changeset['timestamp'];

src/Composer/Repository/Vcs/GitDriver.php

@@ -156,7 +156,7 @@ class GitDriver extends VcsDriver
 
             $composer = JsonFile::parseJson($composer, $resource);
 
-            if (!isset($composer['time'])) {
+            if (empty($composer['time'])) {
                 $this->process->execute(sprintf('git log -1 --format=%%at %s', ProcessExecutor::escape($identifier)), $output, $this->repoDir);
                 $date = new \DateTime('@'.trim($output), new \DateTimeZone('UTC'));
                 $composer['time'] = $date->format('Y-m-d H:i:s');

src/Composer/Repository/Vcs/GitHubDriver.php

@@ -171,7 +171,7 @@ class GitHubDriver extends VcsDriver
             if ($composer) {
                 $composer = JsonFile::parseJson($composer, $resource);
 
-                if (!isset($composer['time'])) {
+                if (empty($composer['time'])) {
                     $resource = $this->getApiUrl() . '/repos/'.$this->owner.'/'.$this->repository.'/commits/'.urlencode($identifier);
                     $commit = JsonFile::parseJson($this->getContents($resource), $resource);
                     $composer['time'] = $commit['commit']['committer']['date'];

src/Composer/Repository/Vcs/HgBitbucketDriver.php

@@ -102,7 +102,7 @@ class HgBitbucketDriver extends VcsDriver
 
             $composer = JsonFile::parseJson($repoData['data'], $resource);
 
-            if (!isset($composer['time'])) {
+            if (empty($composer['time'])) {
                 $resource = $this->getScheme() . '://bitbucket.org/api/1.0/repositories/'.$this->owner.'/'.$this->repository.'/changesets/'.$identifier;
                 $changeset = JsonFile::parseJson($this->getContents($resource), $resource);
                 $composer['time'] = $changeset['timestamp'];

src/Composer/Repository/Vcs/HgDriver.php

@@ -124,7 +124,7 @@ class HgDriver extends VcsDriver
 
             $composer = JsonFile::parseJson($composer, $identifier);
 
-            if (!isset($composer['time'])) {
+            if (empty($composer['time'])) {
                 $this->process->execute(sprintf('hg log --template "{date|rfc3339date}" -r %s', ProcessExecutor::escape($identifier)), $output, $this->repoDir);
                 $date = new \DateTime(trim($output), new \DateTimeZone('UTC'));
                 $composer['time'] = $date->format('Y-m-d H:i:s');

src/Composer/Repository/Vcs/SvnDriver.php

@@ -148,7 +148,7 @@ class SvnDriver extends VcsDriver
 
             $composer = JsonFile::parseJson($output, $this->baseUrl . $resource . $rev);
 
-            if (!isset($composer['time'])) {
+            if (empty($composer['time'])) {
                 $output = $this->execute('svn info', $this->baseUrl . $path . $rev);
                 foreach ($this->process->splitLines($output) as $line) {
                     if ($line && preg_match('{^Last Changed Date: ([^(]+)}', $line, $match)) {