[vala/staging] compiler: fix critical when vala is called without run args

[Rico Tzschichholz <ricotz src gnome org>]

commit a9996877480287308d8273c8469c87fa48b3a3ea
Author: Dr. Michael Lauer <mickey vanille-media de>
Date:   Wed Feb 28 13:14:53 2018 +0100

    compiler: fix critical when vala is called without run args
    
    https://bugzilla.gnome.org/show_bug.cgi?id=793657

 compiler/valacompiler.vala |    8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)
---
diff --git a/compiler/valacompiler.vala b/compiler/valacompiler.vala
index 522b41a..63a567e 100644
--- a/compiler/valacompiler.vala
+++ b/compiler/valacompiler.vala
@@ -570,9 +570,11 @@ class Vala.Compiler {
                }
 
                string[] target_args = { output };
-               string[] target_run_args = run_args.split (" ");
-               foreach (string arg in target_run_args) {
-                       target_args += arg;
+               if (run_args != null) {
+                       string[] target_run_args = run_args.split (" ");
+                       foreach (string arg in target_run_args) {
+                               target_args += arg;
+                       }
                }
 
                try {