fix incorrect vesting remainder behavior

also checks vesting schedule range when calculating

x/colinearcore/math/vesting.go

@@ -1,6 +1,7 @@
 package colinearmath
 
 import (
+	"fmt"
 	"math/big"
 	"time"
 )
@@ -11,11 +12,15 @@ import (
 func CalcAmountVestableLinear(
 	total *big.Int,
 	remaining *big.Int,
-	date time.Time,
+	now time.Time,
 	beginDate time.Time,
 	endDate time.Time,
 ) (*big.Int, error) {
-	timePassed := big.NewInt(date.Unix() - beginDate.Unix())
+	timePassed := big.NewInt(now.Unix() - beginDate.Unix())
+	if timePassed.Cmp(big.NewInt(0)) == -1 {
+		return nil, fmt.Errorf("time %d is out of range (%d, %d)", now.Unix(), beginDate.Unix(), endDate.Unix())
+	}
+
 	totalTime := big.NewInt(endDate.Unix() - beginDate.Unix())
 
 	taken := big.NewInt(0)