fix: prevent from "implementation class is not specified" with documentMatcher

[angelozerr]

fix: prevent from "implementation class is not specified" with documentMatcher

When documentMatcher is not declared in languageMapping, fileTypeMapping, etc, the following exception is thrown https://github.com/JetBrains/intellij-community/blob/def6433a5dd9f0a984cbc6e2835d27c97f2cb5f0/platform/core-api/src/com/intellij/serviceContainer/LazyExtensionInstance.java#L55

We catch this method, but it is cleaner to avoid calling getInstance if documentMatcher is not declared.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 15 lines in your changes missing coverage. Please review.

Project coverage is 23.63%. Comparing base (0b8414c) to head (ba149d9).

Files	Patch %	Lines
...sion/FileNamePatternMappingExtensionPointBean.java	0.00%	5 Missing ⚠️
...n/extension/FileTypeMappingExtensionPointBean.java	0.00%	5 Missing ⚠️
...n/extension/LanguageMappingExtensionPointBean.java	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #347      +/-   ##
==========================================
- Coverage   23.67%   23.63%   -0.05%     
==========================================
  Files         265      265              
  Lines        9093     9111      +18     
  Branches     1243     1243              
==========================================
  Hits         2153     2153              
- Misses       6535     6553      +18     
  Partials      405      405              

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