termstatus: Fix panic for non-terminal runs

Closes #1803

internal/ui/termstatus/status_test.go

@@ -0,0 +1,32 @@
+package termstatus
+
+import "testing"
+
+func TestTruncate(t *testing.T) {
+	var tests = []struct {
+		input  string
+		maxlen int
+		output string
+	}{
+		{"", 80, ""},
+		{"", 0, ""},
+		{"", -1, ""},
+		{"foo", 80, "foo"},
+		{"foo", 4, "foo"},
+		{"foo", 3, "foo"},
+		{"foo", 2, "fo"},
+		{"foo", 1, "f"},
+		{"foo", 0, ""},
+		{"foo", -1, ""},
+	}
+
+	for _, test := range tests {
+		t.Run("", func(t *testing.T) {
+			out := truncate(test.input, test.maxlen)
+			if out != test.output {
+				t.Fatalf("wrong output for input %v, maxlen %d: want %q, got %q",
+					test.input, test.maxlen, test.output, out)
+			}
+		})
+	}
+}