Inputs of Input and Output Label and Expression toggle deleted values

[sebwarnke]

Describe the Bug
During editing input/output expression and label inputs provided by the overlay that pops up when a columns header is clicked a pre-entered value reappears shortly after it was deleted and disappears again.

Steps to Reproduce

1. create a new table
2. click the name cell of an input column
3. enter a value into either Input Expression or Input Label
4. remove the value
5. enter something new shortly after
6. hit backspace (to correct a typo for example)
7. enter something new

in the end this will make the modeler behave strange

Expected Behavior

I expect the deleted values to not reappear.

Environment

Please complete the following information:

• Browser: Chrome 71.0.3578.98
• OS: MacOS Mojave
• Library version: the one used on bpmn.io

Camunda Modeler 2.2.3 shows the same behavior

[barmac]

Thank you for your time preparing the description. If you feel you could help us handle this issue, please be welcome to prepare a pull request with a bugfix.