Fix loading of PDF files with invalid or missing Type3 characters (issue 5039)

[Snuffleupagus]

Fixes #5039.

This PR actually addresses two different Type3 issues:

• The case described in the issue, where we're unable to load all font resources because of invalid data.
  In the file in the issue, the offending font resource is the one for the "space" character. If we just catch the Promise rejection (in evaluator.js) all pages would finish rendering.
  However there would be no spaces present between words, which is thus solved by adding an empty OperatorList to the charProcOperatorList array.
• To fix the issue referenced above, the changes in evaluator.js is actually enough.
  But when I created the test case, I accidentally stumbled on another issue: if a showText command for a Type3 font contains a reference to a character not present in the font, the page won't finish rendering. Hence the changes to canvas.js to address this, hopefully rare, case.

[timvandermeij]

Nice work, I can confirm the fix.

[timvandermeij]

/botio test

[pdfjsbot]

From: Bot.io (Linux)

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Received

Command cmd_test from @timvandermeij received. Current queue size: 0

Live output at: http://107.21.233.14:8877/b2aa1fd13da8075/output.txt

[pdfjsbot]

From: Bot.io (Windows)

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Received

Command cmd_test from @timvandermeij received. Current queue size: 0

Live output at: http://107.22.172.223:8877/8caebec31111cc5/output.txt

[pdfjsbot]

From: Bot.io (Windows)

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Success

Full output at http://107.22.172.223:8877/8caebec31111cc5/output.txt

Total script time: 21.40 mins

• Font tests: Passed
• Unit tests: Passed
• Regression tests: Passed

[pdfjsbot]

From: Bot.io (Linux)

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Success

Full output at http://107.21.233.14:8877/b2aa1fd13da8075/output.txt

Total script time: 23.50 mins

• Font tests: Passed
• Unit tests: Passed
• Regression tests: Passed

[yurydelendik]

/botio makeref

[pdfjsbot]

From: Bot.io (Linux)

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Received

Command cmd_makeref from @yurydelendik received. Current queue size: 0

Live output at: http://107.21.233.14:8877/e678a3e4b22a2d4/output.txt

[pdfjsbot]

From: Bot.io (Windows)

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Received

Command cmd_makeref from @yurydelendik received. Current queue size: 0

Live output at: http://107.22.172.223:8877/237f1aeaf345b4b/output.txt

[yurydelendik]

Thank you for the patch

[pdfjsbot]

From: Bot.io (Windows)

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Success

Full output at http://107.22.172.223:8877/237f1aeaf345b4b/output.txt

Total script time: 21.41 mins

• Lint: Passed
• Make references: Passed
• Check references: Passed

[pdfjsbot]

From: Bot.io (Linux)

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Success

Full output at http://107.21.233.14:8877/e678a3e4b22a2d4/output.txt

Total script time: 23.46 mins

• Lint: Passed
• Make references: Passed
• Check references: Passed