Validate genotype-likelihood error-matrix input

[thierrygosselin]

Summary

The genotype-likelihood error-matrix reader assumed that every input line contained all 16 required fields. Truncated or empty files could therefore cause invalid parsing or division by zero.

This change:

• checks that each row contains 16 fields;
• reports the file and line number for malformed input;
• rejects empty error-matrix files;
• uses a failure exit status for these fatal input errors;
• preserves the existing error-matrix calculation for valid files.

No likelihood model or numerical calculation was changed.