`.handle()` w/ new text yields previous results if AssertionError is raised

When using the same HTML2Text instance, the failure is presisted through future valid strings. Items that it tries to prepend the old text to the new text

- Version by `html2text --version` **2020.1.16**
- Test script
- Python version `python --version` **3.10.11**

## Failing
```
test = "Hellowworld"
test2="Goodbye"

h = HTML2Text()

try:
print(h.handle(test))
except AssertionError:
h.handle(test2)
```
### ouput
```
[...] raise AssertionError(
AssertionError: expected name token at "worldGoodbye"
```
## Working
```
test = "Hellowworld"
test2="Goodbye"

h = HTML2Text()
try:
print(h.handle(test))
except AssertionError:
print("pass")
```

### output
```
pass
```