forward to analysis page (missing analysis)

[jstucke]

• if an analysis did not run for a file, the user is directed to an error page (a page empty except for an error message)
• this is not helpful, so this PR changes this behavior as follows: Instead of showing the error page the user is forwarded back to the analysis page (without selected plugin) and the error is displayed as flash message
• steps to (re)produce the error: Go to some file in a FW, run a "single file analysis" and go back to the root object through the link in the "general information" section

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.85%. Comparing base (058e49f) to head (e52b4b5).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1320      +/-   ##
==========================================
- Coverage   92.42%   91.85%   -0.58%     
==========================================
  Files         379      378       -1     
  Lines       23661    20982    -2679     
==========================================
- Hits        21869    19272    -2597     
+ Misses       1792     1710      -82     

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[maringuu]

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