solve1.m: trap zero Jacobian case

matlab/solve1.m

@@ -121,7 +121,20 @@ for its = 1:maxit
     end
     if rcond_fjac < sqrt(eps)
         fjac2=fjac'*fjac;
-        p=-(fjac2+sqrt(nn*eps)*max(sum(abs(fjac2)))*eye(nn))\(fjac'*fvec);
+        fjac_norm=sum(abs(fjac2));
+        if fjac_norm>0
+            p=-(fjac2+sqrt(nn*eps)*max(fjac_norm)*eye(nn))\(fjac'*fvec);
+        else
+            errorflag = true;
+            errorcode = 5;
+            if nargout<3
+                skipline()
+                dprintf('SOLVE: Iteration %s', num2str(its))
+                disp('Zero Jacobian.')
+                skipline()
+            end
+            return
+        end
     else
         p = -fjac\fvec ;
     end