No lower limit on the MTRG delegation amount

[Gotogu]

Describe the bug
No lower limit on the MTRG delegation amount

To Reproduce

1. Go to candidates.
2. Choose a bucket then click on vote.
3. Fil the delegation amount with 0.000000000000000000000.....00000000000000000001.
4. Send.
   You can fullfil the step 3 with hundreds of zero after the decimal point.

Actual result:

Desktop OS :
Win10