Mask validation fails for single "0" input (regression from v15)

[MatthiasDeBuXerius]

🐞 bug report

Is this a regression?

Yes, it worked in 15.2.3, after upgrading to 20.0.3 it no longer works

Before (Angular v15)
Using mask="1||0,N" (with N being 1-9) allowed typing:

0
0, followed by a digit
1

After upgrade to Angular v20
Typing only 0 fails validation. The mask now requires either:

0, followed by a digit
or 1

Simple 0 is considered invalid.

🔬 Minimal Reproduction

use mask "1||0,N":

<input
      type="text"
      mask="1||0,N"
      [patterns]="customMaskPatterns"
      [dropSpecialCharacters]="false"
      [decimalMarker]="','"
      inputmode="numeric"
    />

with patterns:

public customMaskPatterns = {
    N: { pattern: new RegExp('[0-9]') },
    0: { pattern: new RegExp('0') },
    1: { pattern: new RegExp('1') },
  };

🔥 Exception or Error

none

🌍 Your Environment

Angular Version:

@angular-devkit/schematics      20.3.8
@angular/build                  20.3.8
@angular/cdk                    20.2.11
@angular/cli                    20.3.8
@schematics/angular             20.3.8
rxjs                            7.8.2
typescript                      5.9.3
zone.js                         0.15.1

Anything else relevant?
n/a