Fix fq.gz input detection

Author: jch-13

src/map/input_chunk_reader.rs

@@ -121,9 +121,10 @@ impl InputSource {
         if buf[..2] == GZIP_MAGIC_NUMBER {
             let mut reader = bgzf::Reader::new(src);
             let mut buf = [0; 4];
-            reader
-                .read_exact(&mut buf)
-                .map_err(|_e| Error::InvalidInputType)?;
+            if let Err(_) = reader.read_exact(&mut buf) {
+                // We are going to ignore this error, since we probably got GZ instead of BGZF data.
+                // If that is not the case, potential errors are properly handled elsewhere.
+            }
 
             return if buf == BAM_MAGIC_NUMBER {
                 Ok(Format::Bam)