keep the previous output when there's an error.

so that we don't just see errors 99% of the time.
closes #20

engine.go

@@ -61,12 +61,12 @@ func (e *Engine) Run() *EngineResult {
 	defer termbox.Close()
 	termbox.SetInputMode(termbox.InputAlt)
 
-	var contents []string
+	var contents []string = []string{""}
 
 	for {
 		e.candidates = []string{}
 		e.autocomplete = ""
-		contents = e.getContents()
+		contents = e.getContents(contents)
 		e.makeCandidates()
 		e.setCandidateData()
 
@@ -180,9 +180,16 @@ func (e *Engine) Run() *EngineResult {
 	}
 }
 
-func (e *Engine) getContents() []string {
-	cc, _ := jqrun(e.query.StringGet(), e.json, e.args)
-	return strings.Split(cc, "\n")
+func (e *Engine) getContents(prevContents []string) []string {
+	cc, err := jqrun(e.query.StringGet(), e.json, e.args)
+	if err == nil {
+		return strings.Split("\n"+cc, "\n")
+	} else {
+		return append(
+			strings.Split(cc[0:strings.Index(cc, "\n")], "\n"),
+			prevContents[1:]...,
+		)
+	}
 }
 
 var complicatedKeyRegex = regexp.MustCompile(`\d|\W`)

go.mod

@@ -5,4 +5,5 @@ go 1.14
 require (
 	github.com/mattn/go-runewidth v0.0.9 // indirect
 	github.com/nsf/termbox-go v0.0.0-20200418040025-38ba6e5628f1
+	github.com/stretchr/testify v1.6.1
 )

go.sum

@@ -1,4 +1,14 @@
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/mattn/go-runewidth v0.0.9 h1:Lm995f3rfxdpd6TSmuVCHVb/QhupuXlYr8sCI/QdE+0=
 github.com/mattn/go-runewidth v0.0.9/go.mod h1:H031xJmbD/WCDINGzjvQ9THkh0rPKHF+m2gUSrubnMI=
 github.com/nsf/termbox-go v0.0.0-20200418040025-38ba6e5628f1 h1:lh3PyZvY+B9nFliSGTn5uFuqQQJGuNrD0MLCokv09ag=
 github.com/nsf/termbox-go v0.0.0-20200418040025-38ba6e5628f1/go.mod h1:IuKpRQcYE1Tfu+oAQqaLisqDeXgjyyltCfsaoYN18NQ=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.6.1 h1:hDPOHmpOpP40lSULcqw7IrRb/u7w6RpDC9399XyoNd0=
+github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=