fix(oer): isSafeLength should not accept zero

Since isSafeLength is used to sanitize inputs for methods like readUIntBE, it must not allow a length of zero which will trigger an exception.

Allowing zero also did not match  the type definition for SafeByteLength.

packages/oer-utils/src/lib/util.ts

@@ -8,7 +8,7 @@ export const MAX_SAFE_BYTES = 6
 export type SafeByteLength = 1 | 2 | 3 | 4 | 5 | 6
 
 export const isSafeLength = (length: number): length is SafeByteLength =>
-  isInteger(length) && length >= 0 && length <= MAX_SAFE_BYTES
+  isInteger(length) && length >= 1 && length <= MAX_SAFE_BYTES
 
 const INTEGER_REGEX = /^-?[0-9]+$/
 export function isInteger(value: unknown): boolean {