Index: /issm/trunk-jpl/src/m/classes/model.m
===================================================================
--- /issm/trunk-jpl/src/m/classes/model.m	(revision 23433)
+++ /issm/trunk-jpl/src/m/classes/model.m	(revision 23434)
@@ -128,6 +128,8 @@
 			if isa(md.esa,'double'); md.esa=esa(); end
 			%2017 February 10th
-			if md.settings.solver_residue_threshold==0,
-				md.settings.solver_residue_threshold = 1e-6;
+			if isa(md.settings,'settings'), %this 'isa' verification: 2018 October 24th
+				if md.settings.solver_residue_threshold==0,
+					md.settings.solver_residue_threshold = 1e-6;
+				end
 			end
 			%2017 April 10th