Cosmos-sdk: May cause mint module panic

[dreamer-zq]

Summary of Bug

The parameter MintDenom can be modified through the gov module, so when initiating a parameter modification proposal, the legitimacy of the modified parameter should be checked. Otherwise, once an illegal value is submitted (referring to an illegal denom here, of course, it may be due to a mistake), and the proposal is approved, which may cause panic

Version

master

Steps to Reproduce

1. Submit MintDenom parameter modification proposal
2. Vote on the previous step's proposal

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[dreamer-zq]

Here should check the legality of denom https://github.com/cosmos/cosmos-sdk/blob/5be87e40cef3f58419d76b236c246d3e4032a7a3/x/mint/internal/types/params.go#L71
or add an interface method Validate(key,value []string) in ParamSet https://github.com/cosmos/cosmos-sdk/blob/5be87e40cef3f58419d76b236c246d3e4032a7a3/x/params/subspace/paramset.go#L19

[fedekunze]

I recall that parameter validation is still a TODO that we need to address. cc: @alexanderbez.

[fedekunze]

dup of #3473