subpaving assertion violation at ../src/util/old_vector.h Line: 370

Hi,
For this formula:
```
(assert (distinct (+ 1.0 (^ 0.5 70.0)) 1.0))
(check-sat-using subpaving)
```
Z3  throws out an assertion violation:
```
ASSERTION VIOLATION
File: ../src/util/old_vector.h
Line: 370
idx < size()
(C)ontinue, (A)bort, (S)top, (T)hrow exception, Invoke (G)DB
```

OS: Ubuntu 18.04
Commit: aaf2c3b
