Fix index out of bounds error during Transform

2 files changed, 11 insertions, 1 deletions

diff --git a/src/tokenizer.go b/src/tokenizer.go
index c187529b..bc1ca3a4 100644
--- a/src/tokenizer.go
+++ b/src/tokenizer.go
@@ -186,7 +186,13 @@ func Transform(tokens []Token, withNth []Range) *Transformed {
 			}
 		}
 		whole += part
-		transTokens[idx] = Token{&part, tokens[minIdx].prefixLength}
+		var prefixLength int
+		if minIdx < numTokens {
+			prefixLength = tokens[minIdx].prefixLength
+		} else {
+			prefixLength = 0
+		}
+		transTokens[idx] = Token{&part, prefixLength}
 	}
 	return &Transformed{
 		whole: &whole,
diff --git a/src/tokenizer_test.go b/src/tokenizer_test.go
index ed77efe9..1ae0c7ee 100644
--- a/src/tokenizer_test.go
+++ b/src/tokenizer_test.go
@@ -95,3 +95,7 @@ func TestTransform(t *testing.T) {
 		}
 	}
 }
+
+func TestTransformIndexOutOfBounds(t *testing.T) {
+	Transform([]Token{}, splitNth("1"))
+}