Don't choke when unit size is not decimal-compatible

rattail_corepos/importing/model.py

@@ -140,7 +140,10 @@ class ProductImporter(importing.model.ProductImporter):
 
         unit_size = None
         if 'size' in core_data and core_data['size'] is not None:
+            try:
                 unit_size = decimal.Decimal(core_data['size'])
+            except decimal.InvalidOperation:
+                pass
 
         uom_abbrev = core_data.get('unitofmeasure')