Fix invalid results in output

[AndreaGuarracino]

This fixes an annoying bug that has been strangely hidden for a long time that affects all output formats. When a target range is not found in a query, no results should be emitted. By not doing any checks on the results, a lot of invalid ranges were returned (wrong ranges, ranges with length 0, or empty projected CIGAR strings).

I report an example with the PAF format as output that shows also the wrong target ranges (outside the interval used to query the alignments):

# number of wrong results
impg -p chr6.y1.s10p95.paf -r grch38#chr6:31972057-32055418 -P | grep 'cg:Z:$' -c     
28092

# number of valid results
impg -p chr6.y1.s10p95.paf -r grch38#chr6:31972057-32055418 -P | grep 'cg:Z:$' -cv
232

# A few invalid results
impg -p chr6.y1.s10p95.paf -r grch38#chr6:31972057-32055418 -P | grep 'cg:Z:$' | head | column -t     
HG03579#2#JAGYVT010000047.1  26762912  15990000  16040000  +  grch38#chr6  170805979  15961422  16011615  0  0  255  gi:f:NaN  bi:f:NaN  cg:Z:
HG02080#1#JAHEOW010000032.1  56349618  15980000  16030000  +  grch38#chr6  170805979  15961437  16011454  0  0  255  gi:f:NaN  bi:f:NaN  cg:Z:
NA18906#2#JAHEON010000095.1  24213007  15940000  15990000  +  grch38#chr6  170805979  15962138  16012310  0  0  255  gi:f:NaN  bi:f:NaN  cg:Z:
HG01071#2#JAHBCE010000081.1  25027143  15930000  15980000  +  grch38#chr6  170805979  15962428  16012508  0  0  255  gi:f:NaN  bi:f:NaN  cg:Z:
HG03486#1#JAHEOQ010000114.1  19325645  0         8340000   +  grch38#chr6  170805979  15962549  16012596  0  0  255  gi:f:NaN  bi:f:NaN  cg:Z:
HG01952#2#JAHAMD010000016.1  59464697  15980000  16030000  +  grch38#chr6  170805979  15962782  16012783  0  0  255  gi:f:NaN  bi:f:NaN  cg:Z:
HG02723#2#JAHEOT010000038.1  23679014  10940000  10990000  +  grch38#chr6  170805979  15962796  16012895  0  0  255  gi:f:NaN  bi:f:NaN  cg:Z:
HG00438#1#JAHBCB010000067.1  24808650  15980000  16030000  +  grch38#chr6  170805979  15963320  16013504  0  0  255  gi:f:NaN  bi:f:NaN  cg:Z:
HG02559#2#JAGYVJ010000064.1  59272483  15940000  15990000  +  grch38#chr6  170805979  15963723  16013901  0  0  255  gi:f:NaN  bi:f:NaN  cg:Z:
HG02486#2#JAGYVL010000026.1  60776310  15850000  15900000  +  grch38#chr6  170805979  15963767  16013866  0  0  255  gi:f:NaN  bi:f:NaN  cg:Z: