Try to avoid a crash in freqcal.f90 when data is all zeros.

lib/freqcal.f90

@@ -41,6 +41,7 @@ subroutine freqcal(id2,k,nkhz,noffset,ntol,line)
   endif
   smax=0.
   s=0.
+  ipk=-99
   do i=ia,ib
      s(i)=real(cx(i))**2 + aimag(cx(i))**2
      if(s(i).gt.smax) then
@@ -49,6 +50,7 @@ subroutine freqcal(id2,k,nkhz,noffset,ntol,line)
      endif
   enddo
 
+  if(ipk.ge.1) then
     call peakup(s(ipk-1),s(ipk),s(ipk+1),dx)
     fpeak=df * (ipk+dx)
     ap=(fpeak/fs+1.0/(2.0*NFFT))
@@ -67,6 +69,12 @@ subroutine freqcal(id2,k,nkhz,noffset,ntol,line)
     ave=xsum/nsum
     snr=db(smax/ave)
     pave=db(ave) + 8.0
+  else
+    snr=-99.9
+    pave=-99.9
+    fpeak=-99.9
+    ferr=-99.9
+  endif
   cflag=' '
   if(snr.lt.20.0) cflag='*'
   n=n+1