Fix highlighting of regions that are matched multiple times

Fix #3596

src/result.go

@@ -138,7 +138,9 @@ func (result *Result) colorOffsets(matchOffsets []Offset, theme *tui.ColorTheme,
 		for i := off[0]; i < off[1]; i++ {
 			// Negative of 1-based index of itemColors
 			// - The extra -1 means highlighted
-			cols[i] = cols[i]*-1 - 1
+			if cols[i] >= 0 {
+				cols[i] = cols[i]*-1 - 1
+			}
 		}
 	}
 

src/result_test.go

@@ -120,7 +120,7 @@ func TestColorOffset(t *testing.T) {
 	//   ++++++++        ++++++++++
 	// --++++++++--    --++++++++++---
 
-	offsets := []Offset{{5, 15}, {25, 35}}
+	offsets := []Offset{{5, 15}, {10, 12}, {25, 35}}
 	item := Result{
 		item: &Item{
 			colors: &[]ansiOffset{