title: Argument of type 'number | undefined' is not assignable to parameter of type 'string'
body: <p>I am getting following errors:</p>
  <pre><code>const validateOptions: ChildFormOptionProps
  Argument of type 'number | undefined' is not assignable to parameter of type 'string'.
    Type 'undefined' is not assignable to type 'string'.ts(2345)
  </code></pre>
  <p>Here is my ts code : getting error at <code>&quot;parseInt(validateOptions.minlength)&quot;</code></p>
  <pre><code>username: (control: AbstractControl): { [key: string]: ValidatorFn } | null =&gt; {
              const validateOptions = PatientFormService.controlProps['username'].options;
              if (Object.keys(validateOptions).length) {
                  if (control.value &amp;&amp; control.value.length &lt; parseInt(validateOptions.minlength)) {
                      control.setErrors({ 'incorrect': true });
                      return control.errors;
                  }
              }
              return null;
          },
  </code></pre>
  <p>any suggestion to fix this issue?</p>