Editor: fix highlighting of search results in scrolbar

the QTextBlock::firstLine function takes into account whether previous
blocks are visible.

Fixes: QTCREATORBUG-32332
Change-Id: Id0d16274202d46d62f7cf0a1919e86dc82c58fc8
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>

src/plugins/texteditor/texteditor.cpp

@@ -8236,7 +8236,7 @@ void TextEditorWidgetPrivate::addSearchResultsToScrollBar(
                 }
             } else {
                 m_highlightScrollBarController->addHighlight(
-                    {category, block.blockNumber(), color, prio});
+                    {category, block.firstLineNumber(), color, prio});
             }
         }
     }