Make sure pop() is called when Callback errors in on(...) function

CHANGELOG.md

@@ -11,6 +11,7 @@
 - fix within() to also restore the working-path when the given callback throws a Exception [#1463]
 - `pcntl_fork` is blacklisted per default on ubuntu lts boxes. make sure deployer doesnt emit a warning in this case [#1476]
 - Update silverstripe recipe to support silverstripe 4
+- Make sure Context::pop() is called when Callback errors in on(...) function [#1513]
 
 ## v6.0.5
 [v6.0.4...v6.0.5](https://github.com/deployphp/deployer/compare/v6.0.4...v6.0.5)
@@ -344,6 +345,7 @@
 - Fixed typo3 recipe
 - Fixed remove of shared dir on first deploy
 
+[#1513]: https://github.com/deployphp/deployer/pull/1513
 [#1481]: https://github.com/deployphp/deployer/issues/1481
 [#1476]: https://github.com/deployphp/deployer/pull/1476
 [#1472]: https://github.com/deployphp/deployer/pull/1472

src/functions.php

@@ -372,9 +372,12 @@ function on($hosts, callable $callback)
 
     foreach ($hosts as $host) {
         if ($host instanceof Host) {
-            Context::push(new Context($host, $input, $output));
-            $callback($host);
-            Context::pop();
+            try {
+                Context::push(new Context($host, $input, $output));
+                $callback($host);
+            } finally {
+                Context::pop();
+            }
         } else {
             throw new \InvalidArgumentException("Function on can iterate only on Host instances.");
         }