Fix parsing problem#3

Hi! Thanks for your solution! I've faced a problem with some cases and want to share it with you. Let's see the example: My date mask: `"##.##.####"` and I paste the string `"sometext"`. The result is `".."` It looks strange. Or if I have mask `"##.##.####"` and I past the string `"12andtext"`. The result is `"12.."` One more example: `"(###)"` and I paste the string `"sometext"`. The result is `"()"` I fixed this case and added some tests. I expect that in the first case I get empty string and in the second case I get `"12."` I suggest to stop parsing if current value is empty. Before the fix <img width="1116" alt="Screenshot 2022-01-11 at 12 25 33" src="https://user-images.githubusercontent.com/22646611/148917687-6b421740-8e98-4a8f-9271-2d3b4a002d23.png">