[gnome-builder] launcher: use NULL to specify g_environ_unsetenv()

[Christian Hergert <chergert src gnome org>]

commit d4b2d296bf436750e5ca3159ccd57ccd6f444caa
Author: Christian Hergert <chergert redhat com>
Date:   Tue Jan 16 00:41:59 2018 -0800

    launcher: use NULL to specify g_environ_unsetenv()
    
    This is useful to clear existing values.

 src/libide/subprocess/ide-subprocess-launcher.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/src/libide/subprocess/ide-subprocess-launcher.c b/src/libide/subprocess/ide-subprocess-launcher.c
index cca7fd319..ee374bb0c 100644
--- a/src/libide/subprocess/ide-subprocess-launcher.c
+++ b/src/libide/subprocess/ide-subprocess-launcher.c
@@ -663,7 +663,10 @@ ide_subprocess_launcher_setenv (IdeSubprocessLauncher *self,
   g_return_if_fail (IDE_IS_SUBPROCESS_LAUNCHER (self));
   g_return_if_fail (key != NULL);
 
-  priv->environ = g_environ_setenv (priv->environ, key, value, replace);
+  if (value != NULL)
+    priv->environ = g_environ_setenv (priv->environ, key, value, replace);
+  else
+    priv->environ = g_environ_unsetenv (priv->environ, key);
 }
 
 void