Fix char vs. char* mismatch

Passing '\0' as a "%s" argument to *printf isn't a good idea...

Change-Id: Ia98395c058863be60550da466a7a59352f2b8b1b
Signed-off-by: Bernhard Rosenkränzer <Bernhard.Rosenkranzer@linaro.org>
diff --git a/src/main.cpp b/src/main.cpp
index 4540800..f75b9b2 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -440,7 +440,7 @@
 				break;
 
 			case 'w': /* measure workload */
-				sprintf(workload, "%s", optarg ? optarg :'\0' );
+				sprintf(workload, "%s", optarg ? optarg : "\0" );
 				break;
 			case 'q':
 				if(freopen("/dev/null", "a", stderr))