Fix indexing for out of bound only

(cherry picked from commit 1946eb5)

Author: domfournier

simpeg/directives/_vector_models.py

@@ -143,7 +143,9 @@ def endIter(self):
             if np.any(out_bound):
                 scale = upper_bound / amplitude
                 for ind in indices:
-                    model[ind] *= scale
+                    vec = model[ind]
+                    vec[out_bound] *= scale[out_bound]
+                    model[ind] = vec
 
                 self.invProb.model = model
                 self.opt.xc = model