fix for masking with -ve threshold

meloptions.cc

@@ -118,9 +118,6 @@ MelodicOptions* MelodicOptions::gopt = NULL;
 					cerr << "WARNING: melodic denoising is deprecated, please use fsl_regfilt instead!" <<endl;
     		} 
   		}
-  		if (threshold.value()<=0){
-    		use_mask.set_T(false);
-  		}
   		if (output_all.value()){
     		output_unmix.set_T(true);
     		output_MMstats.set_T(true);