UriQuery.c: Fix out-of-bounds-write in ComposeQuery and ...Ex

Reported by Google Autofuzz team
	void testPervertedQueryString() {
		helperTestQueryString("http://example.org/?&&=&&&=&&&&==&===&====", 5);
	}

	void testPervertedQueryString() {
		helperTestQueryString("http://example.org/?&&=&&&=&&&&==&===&====", 5);
	}
