validate per_page before page

plus an additional check just in case
Closes #1688

rpc/core/pipe.go

@@ -125,6 +125,10 @@ func SetEventBus(b *types.EventBus) {
 }
 
 func validatePage(page, perPage, totalCount int) int {
+	if perPage < 1 {
+		return 1
+	}
+
 	pages := ((totalCount - 1) / perPage) + 1
 	if page < 1 {
 		page = 1

rpc/core/pipe_test.go

@@ -15,6 +15,8 @@ func TestPaginationPage(t *testing.T) {
 		page       int
 		newPage    int
 	}{
+		{0, 0, 1, 1},
+
 		{0, 10, 0, 1},
 		{0, 10, 1, 1},
 		{0, 10, 2, 1},

rpc/core/tx.go

@@ -189,8 +189,8 @@ func TxSearch(query string, prove bool, page, perPage int) (*ctypes.ResultTxSear
 	}
 
 	totalCount := len(results)
-	page = validatePage(page, perPage, totalCount)
 	perPage = validatePerPage(perPage)
+	page = validatePage(page, perPage, totalCount)
 	skipCount := (page - 1) * perPage
 
 	apiResults := make([]*ctypes.ResultTx, cmn.MinInt(perPage, totalCount-skipCount))