Fix error-checking typo in check_TSCurrentConfig().

The code failed to detect an out-of-memory failure.

Xi Wang

src/backend/utils/cache/ts_cache.c

@@ -642,7 +642,7 @@ check_TSCurrentConfig(char **newval, void **extra, GucSource source)
 		free(*newval);
 		*newval = strdup(buf);
 		pfree(buf);
-		if (!newval)
+		if (!*newval)
 			return false;
 	}