Make report renderText() return Optional

[dwalluck]

No description provided.

[codecov]

Codecov Report

Merging #211 into master will increase coverage by 0.03%.
The diff coverage is 90.90%.

@@             Coverage Diff              @@
##             master     #211      +/-   ##
============================================
+ Coverage     68.99%   69.02%   +0.03%     
  Complexity      619      619              
============================================
  Files            38       38              
  Lines          3032     3035       +3     
  Branches        376      376              
============================================
+ Hits           2092     2095       +3     
  Misses          764      764              
  Partials        176      176              

Impacted Files	Coverage Δ	Complexity Δ
...java/org/jboss/pnc/build/finder/report/Report.java	95.00% <85.71%> (+0.26%)	15.00 <4.00> (ø)
...a/org/jboss/pnc/build/finder/report/GAVReport.java	95.65% <100.00%> (ø)	10.00 <1.00> (ø)
.../org/jboss/pnc/build/finder/report/HTMLReport.java	93.92% <100.00%> (ø)	45.00 <1.00> (ø)
...a/org/jboss/pnc/build/finder/report/NVRReport.java	100.00% <100.00%> (ø)	6.00 <1.00> (ø)

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