Made chip_details do something more benign when the user gives an empty

rectangle.

dlib/image_transforms/interpolation.h

@@ -1757,6 +1757,12 @@ namespace dlib
         void compute_dims_from_size (
             unsigned long size
         ) 
+        {
+            if (rect.is_empty())
+            {
+                cols = rows = std::round(std::sqrt((double)size));
+            }
+            else
             {
                 const double relative_size = std::sqrt(size/(double)rect.area());
                 rows = static_cast<unsigned long>(rect.height()*relative_size + 0.5);
@@ -1764,6 +1770,7 @@ namespace dlib
                 rows = std::max(1ul,rows);
                 cols = std::max(1ul,cols);
             }
+        }
     };
 
 // ----------------------------------------------------------------------------------------