PHP 7.4: test failures

Fix the test failures for PHP 7.3/7.4

https://www.drupal.org/pift-ci-job/1727787
https://www.drupal.org/pift-ci-job/1727786

Examples of ones that are not part of the Date module fixes referenced in comment #1 #3164491-1: PHP 7.4: test failures

exception: [Notice] Line 617 of modules/field/field.crud.inc:
Trying to access array offset on value of type null

exception: [Notice] Line 617 of modules/field/field.crud.inc:
Trying to access array offset on value of type null
file_feeds_processor_targets
file_feeds_processor_targets
✗
list_feeds_processor_targets
exception: [Notice] Line 17 of sites/all/modules/feeds/mappers/list.inc:
Trying to access array offset on value of type null

exception: [Notice] Line 17 of sites/all/modules/feeds/mappers/list.inc:
Trying to access array offset on value of type null
✗
number_feeds_processor_targets
exception: [Notice] Line 22 of sites/all/modules/feeds/mappers/number.inc:
Trying to access array offset on value of type null

exception: [Notice] Line 22 of sites/all/modules/feeds/mappers/number.inc:
Trying to access array offset on value of type null
✗
taxonomy_feeds_processor_targets
exception: [Notice] Line 65 of sites/all/modules/feeds/mappers/taxonomy.inc:
Trying to access array offset on value of type null

exception: [Notice] Line 65 of sites/all/modules/feeds/mappers/taxonomy.inc:
Trying to access array offset on value of type null
✗
text_feeds_processor_targets
exception: [Notice] Line 22 of sites/all/modules/feeds/mappers/text.inc:
Trying to access array offset on value of type null

exception: [Notice] Line 22 of sites/all/modules/feeds/mappers/text.inc:
Trying to access array offset on value of type null

phpcs -p --standard=PHPCompatibility --extensions=php,module,inc,install,test,profile,theme .

FILE: feeds.module
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FOUND 0 ERRORS AND 1 WARNING AFFECTING 1 LINE
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 1376 | WARNING | Since PHP 7.0, functions inspecting arguments, like func_get_args(), no longer report the original value as passed to a parameter, but will instead provide the current value. The parameter "$data" was used, and possibly changed (by reference), on line
      |         | 1375.
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