usage: do not print trailing space for commands which have no arguments

function                                             old     new   delta
bb_show_usage                                        120     130     +10

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/libbb/appletlib.c b/libbb/appletlib.c
index 769b788..f155d09 100644
--- a/libbb/appletlib.c
+++ b/libbb/appletlib.c
@@ -169,8 +169,11 @@
 		else {
 			full_write2_str("\nUsage: ");
 			full_write2_str(applet_name);
-			full_write2_str(" ");
-			full_write2_str(p);
+			if (p[0]) {
+				if (p[0] != '\n')
+					full_write2_str(" ");
+				full_write2_str(p);
+			}
 			full_write2_str("\n");
 		}
 		if (ENABLE_FEATURE_CLEAN_UP)