2 fixes: 1. Additional check  of the pointer in the destuctor of the class 2. Small fix in the tracking part - step size and the mass    switched.
2 fixes:
1. Additional check  of the pointer in the destuctor of the class
2. Small fix in the tracking part - step size and the mass
   switched.


coppedis/AliRoot,alisw/AliRoot,miranov25/AliRoot,coppedis/AliRoot,mkrzewic/AliRoot,jgrosseo/AliRoot,jgrosseo/AliRoot,alisw/AliRoot,ecalvovi/AliRoot,sebaleh/AliRoot,ecalvovi/AliRoot,jgrosseo/AliRoot,shahor02/AliRoot,mkrzewic/AliRoot,miranov25/AliRoot,ecalvovi/AliRoot,shahor02/AliRoot,sebaleh/AliRoot,coppedis/AliRoot,jgrosseo/AliRoot,miranov25/AliRoot,ecalvovi/AliRoot,ecalvovi/AliRoot,miranov25/AliRoot,ALICEHLT/AliRoot,shahor02/AliRoot,shahor02/AliRoot,coppedis/AliRoot,jgrosseo/AliRoot,sebaleh/AliRoot,miranov25/AliRoot,mkrzewic/AliRoot,shahor02/AliRoot,ALICEHLT/AliRoot,ecalvovi/AliRoot,jgrosseo/AliRoot,mkrzewic/AliRoot,sebaleh/AliRoot,alisw/AliRoot,alisw/AliRoot,shahor02/AliRoot,alisw/AliRoot,coppedis/AliRoot,shahor02/AliRoot,ecalvovi/AliRoot,mkrzewic/AliRoot,coppedis/AliRoot,sebaleh/AliRoot,mkrzewic/AliRoot,ALICEHLT/AliRoot,miranov25/AliRoot,coppedis/AliRoot,miranov25/AliRoot,alisw/AliRoot,alisw/AliRoot,miranov25/AliRoot,coppedis/AliRoot,sebaleh/AliRoot,mkrzewic/AliRoot,ALICEHLT/AliRoot,ALICEHLT/AliRoot,jgrosseo/AliRoot,sebaleh/AliRoot,ALICEHLT/AliRoot,ALICEHLT/AliRoot,alisw/AliRoot