feat: update executeProposal

Author: iavl

src/ProxyAdminMultiSig.sol

@@ -112,6 +112,10 @@ contract ProxyAdminMultiSig is IErrors {
 
     /// @dev executes a proposal
     function executeProposal(uint256 proposalId) external onlyOwner {
+        if (!_isPendingProposal(proposalId)) {
+            revert NotPendingProposal();
+        }
+
         Proposal storage p = _proposals[proposalId];
         if (p.approvalCount < _threshold) {
             revert NotEnoughApproval();

test/ProxyAdminMultiSig.t.sol

@@ -514,13 +514,25 @@ contract MultiSigTest is IErrors, Test, Utils {
         vm.expectRevert(NotOwner.selector);
         multiSig.executeProposal(proposalId);
 
-        // case 2: not enough approval
+        // case 2: proposal not exist
+        vm.expectRevert(NotPendingProposal.selector);
+        vm.prank(alice);
+        multiSig.executeProposal(200);
+
+        // case 3: not enough approval
         vm.prank(alice);
         multiSig.approveProposal(proposalId);
 
         vm.expectRevert(NotEnoughApproval.selector);
         vm.prank(bob);
         multiSig.executeProposal(proposalId);
+
+        // case 4: can't execute deleted proposal
+        vm.prank(bob);
+        multiSig.deleteProposal(proposalId);
+        vm.expectRevert(NotPendingProposal.selector);
+        vm.prank(charlie);
+        multiSig.executeProposal(proposalId);
     }
 
     function testGetAllProposals() public {