Octave: error() must be called with an argument

Examples/test-suite/octave/voidtest_runme.m

@@ -27,16 +27,16 @@ end_try_catch
 v1 = voidtest.vfunc1(f);
 v2 = voidtest.vfunc2(f);
 if (swig_this(v1) != swig_this(v2))
-    error
+    error("failed");
 endif
 
 v3 = voidtest.vfunc3(v1);
 if (swig_this(v3) != swig_this(f))
-    error
+    error("failed");
 endif
 v4 = voidtest.vfunc1(f);
 if (swig_this(v4) != swig_this(v1))
-    error
+    error("failed");
 endif