dont increase the allocated size of vec (#10701)

substrate/frame/support/src/storage/bounded_vec.rs

@@ -222,16 +222,17 @@ impl<T, S: Get<u32>> BoundedVec<T, S> {
 	/// Returns `true` if the item was inserted.
 	pub fn force_insert_keep_left(&mut self, index: usize, element: T) -> bool {
 		// Check against panics.
-		if Self::bound() < index || self.len() < index {
+		if Self::bound() < index || self.len() < index || Self::bound() == 0 {
 			return false
 		}
 		// Noop condition.
 		if Self::bound() == index && self.len() <= Self::bound() {
 			return false
 		}
-		// Cannot panic since self.len() >= index;
+		// Cannot panic since `Self.bound() > 0`
+		self.0.truncate(Self::bound() - 1);
+		// Cannot panic since `self.len() >= index`;
 		self.0.insert(index, element);
-		self.0.truncate(Self::bound());
 		true
 	}