Logic for enabling/disabling the QAM frequency plan field is flawed.

The field should be enabled when "tune QAM instead of ATSC..." is ticked and disabled when "tune QAM instead of ATSC..." is not ticked.

Currently after scanning, the field is automatically enabled, regardless of whether "tune QAM instead of ATSC..." is ticked or not.

h4. Steps to Reproduce
1. Open TV Server configuration.
2. Go to the scanning section for an ATSC tuner.
3. Untick "tune QAM instead of ATSC..." (QAM frequency plan should be disabled.
4. Start a scan.
5. Cancel the scan.

==> The QAM frequency plan field is enabled even though "tune QAM instead of ATSC..." is disabled.