Catch runtime exception while initializing Composer to make sure a missing composer.json does not fail >tryComposer, refs #11133

src/Composer/Console/Application.php

@@ -17,6 +17,7 @@ use Composer\Util\Filesystem;
 use Composer\Util\Platform;
 use Composer\Util\Silencer;
 use LogicException;
+use RuntimeException;
 use Seld\Signal\SignalHandler;
 use Symfony\Component\Console\Application as BaseApplication;
 use Symfony\Component\Console\Exception\CommandNotFoundException;
@@ -512,6 +513,10 @@ class Application extends BaseApplication
                 if ($required) {
                     throw $e;
                 }
+            } catch (RuntimeException $e) {
+                if ($required) {
+                    throw $e;
+                }
             }
         }