Fix possible NULL deref in run() error handling

When we added support for using popen() to run(), to log the output, we
forgot to update the error handling path.  Found by Coverity Scan.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/exec.c

@@ -97,12 +97,14 @@ static int do_redirect(void)
  */
 int run(char *cmd, char *log)
 {
+	char *args[NUM_ARGS + 1] = { 0 };
 	int status, result, i = 0;
-	char *args[NUM_ARGS + 1], *arg;
 	char *backup = NULL;
 	pid_t pid;
 
 	if (!log) {
+		char *arg;
+
 		/* We must create a copy that is possible to modify. */
 		backup = arg = strdup(cmd);
 		if (!arg)
@@ -164,7 +166,7 @@ int run(char *cmd, char *log)
 
 		_exit(rc);
 	} else if (-1 == pid) {
-		_pe("%s", args[0]);
+		_pe("%s", !log ? args[0] : cmd);
 		if (backup)
 			free(backup);