ECL error with symbolic sum containing real

<div id="comment:0"></div>


```
sage: var('k, n')
sage: sum(k^2015/1.0001^k,k,1,n)
```
gives repeated

```
;;; Detected access to protected memory, also kwown as 'bus or segmentation fault'.
;;; Jumping to the outermost toplevel prompt
```


CC:  @behackl

Component: **symbolics**

_Issue created by migration from https://trac.sagemath.org/ticket/19909_

