Fix een boel deprecations

[NathanHuisman]

Hopelijk worden onze logs nu minder volgespamd :)

[sentry-io[bot]]

🔍 Existing Issues For Review

Your pull request is modifying functions with the following pre-existing issues:

📄 File: lib/entity/corvee/CorveeTaak.php

Function	Unhandled Issue
CsrDelft\entity\corvee\CorveeTaak::getLaatstGemaildDate	ErrorException: Deprecated: strpos(): Passing null to parameter #1 ($haystack) of type string is deprecated /lib/entity/corvee/CorveeTaak.php... Event Count: 392

📄 File: lib/view/formulier/invoervelden/InputField.php (Click to Expand)

| Function | Unhandled Issue | | :------- | :----- | | **`CsrDelft\view\formulier\invoervelden\InputField::getInputAttribute`** | [**ErrorException: Deprecated: htmlspecialchars(): Passing null to parameter #1 ($string) of type string is deprecated**](https://csrdelft.sentry.io/issues/5345954921/?referrer=github-open-pr-bot) /lib/view/formulier/invoervelden/InputField.php in...
`Event Count:` **131** | | **`CsrDelft\view\formulier\invoervelden\TextField::getInputAttribute`** | [**ErrorException: Deprecated: htmlspecialchars(): Passing null to parameter #1 ($string) of type string is deprecated**](https://csrdelft.sentry.io/issues/5353355009/?referrer=github-open-pr-bot) /lib/view/formulier/invoervelden/InputField.php in...
`Event Count:` **34** |

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[sonarcloud[bot]]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud