fix: empty string causes panic

stringwrap.go

@@ -89,7 +89,11 @@ type WrappedStringSeq struct {
 
 // lastWrappedLine pulls the last wrapped line that has been parsed
 func (s *WrappedStringSeq) lastWrappedLine() *WrappedString {
-	return &s.WrappedLines[len(s.WrappedLines)-1]
+	n := len(s.WrappedLines)
+	if n == 0 {
+		return nil
+	}
+	return &s.WrappedLines[n-1]
 }
 
 // appendWrappedSeq adds a new WrappedString to the existing slice
@@ -489,7 +493,7 @@ func stringWrap(
 	// remove the last new line from the wrapped buffer
 	// if the last line is not a hard break.
 	lastWrappedLine := wrappedStringSeq.lastWrappedLine()
-	if !lastWrappedLine.IsHardBreak {
+	if lastWrappedLine != nil && !lastWrappedLine.IsHardBreak {
 		stateMachine.buffer.Truncate(stateMachine.buffer.Len() - 1)
 		lastWrappedLine.LastSegmentInOrig = true
 	}

stringwrap_test.go

@@ -129,13 +129,24 @@ func TestStringWrap(t *testing.T) {
 			trimWhitespace: true,
 			splitWord:      true,
 		},
+		{
+			input:          "",
+			wrapped:        "",
+			limit:          5,
+			trimWhitespace: true,
+			splitWord:      true,
+		},
 	}
 
 	for idx, tt := range tests {
 		t.Run(fmt.Sprintf("Wrapped String Test %d", idx+1), func(t *testing.T) {
 			wrapped, seq, err := wrapString(tt)
+			expectedLines := 0
+			if wrapped != "" {
+				expectedLines = len(strings.Split(wrapped, "\n"))
+			}
 			assert.Nil(t, err)
-			assert.Equal(t, len(seq.WrappedLines), len(strings.Split(wrapped, "\n")))
+			assert.Equal(t, expectedLines, len(seq.WrappedLines))
 			assert.Equal(t, tt.wrapped, wrapped)
 		})
 	}