Bug 17803 - Fix both test case and validation logic

The previous commit had errors in both the test case and
the validation logic.  The test case was missing a trailing
comma before the previous one, so we weren't testing the
signature we thought we were.

The validation logic was wrong because if the type was not valid,
we'd drop through the entire if clause, and thus skip returning
an error code, and accept the signature.

dbus/dbus-marshal-validate-util.c

@@ -227,7 +227,7 @@ _dbus_marshal_validate_test (void)
     "not a valid signature",
     "123",
     ".",
-    "("
+    "(",
     "a{(ii)i}" /* https://bugs.freedesktop.org/show_bug.cgi?id=17803 */
   };
 

dbus/dbus-marshal-validate.c

@@ -246,14 +246,15 @@ _dbus_validate_signature_with_reason (const DBusString *type_str,
 	    }
         }
 
-      if (last == DBUS_DICT_ENTRY_BEGIN_CHAR &&
-          _dbus_type_is_valid (*p) &&
-          !dbus_type_is_basic (*p))
+      if (last == DBUS_DICT_ENTRY_BEGIN_CHAR)
         {
-          result = DBUS_INVALID_DICT_KEY_MUST_BE_BASIC_TYPE;
-          goto out;
+          if (!(_dbus_type_is_valid (*p) && dbus_type_is_basic (*p)))
+            {
+              result = DBUS_INVALID_DICT_KEY_MUST_BE_BASIC_TYPE;
+              goto out;
+            }
         }
-        
+
       last = *p;
       ++p;
     }