PHP 7 incompatibility

We need to upgrade our web server to PHP 7, but SiteOrigin Widgets Bundle is causing three PHP compatibility warnings and three errors. I’ve pasted them below.

I posted about this on the WordPress plugin forum under Support, but did not receive a response. Now my post has been deleted. I don’t know why.

We’d greatly appreciate advice, or at least some explanation as to why this is an inappropriate question, if it is one.

FILE: /wp-content/plugins/so-widgets-bundle/base/inc/lib/Less/Parser.php
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FOUND 0 ERRORS AND 3 WARNINGS AFFECTING 3 LINES
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  93 | WARNING | INI directive 'mbstring.internal_encoding' is deprecated since PHP 5.6.
  94 | WARNING | INI directive 'mbstring.internal_encoding' is deprecated since PHP 5.6.
 229 | WARNING | INI directive 'mbstring.internal_encoding' is deprecated since PHP 5.6.
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FILE: /wp-content/plugins/so-widgets-bundle/base/inc/lib/Less/SourceMap/Base64VLQ.php
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FOUND 3 ERRORS AFFECTING 1 LINE
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 156 | ERROR | Bitwise shifts by negative number will throw an ArithmeticError in PHP 7.0
 156 | ERROR | Bitwise shifts by negative number will throw an ArithmeticError in PHP 7.0
 156 | ERROR | Bitwise shifts by negative number will throw an ArithmeticError in PHP 7.0
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