fix: isHex string extension function refactoring

Author: JeneaVranceanu

Sources/Web3Core/Utility/String+Extension.swift

@@ -137,7 +137,17 @@ extension String {
     }
 
     public var isHex: Bool {
-        stripHexPrefix().reduce(true, { $0 && $1.isHexDigit } )
+        var _str = self.trim()
+        if _str.isEmpty {
+            return false
+        }
+        _str = _str.stripHexPrefix()
+        for char in _str {
+            if !char.isHexDigit {
+                return false
+            }
+        }
+        return true
     }
 }
 

Tests/web3swiftTests/localTests/ABIDecoderSliceTests.swift

@@ -80,7 +80,7 @@ final class ABIDecoderSliceTests: XCTestCase {
         var resultArray = [BigUInt]()
         for i in 0..<2 {
             guard let data = returnData[i][1] as? Data,
-                  let balance = try? erc20_balanceof.decodeReturnData(data)["0"] as? BigUInt else {
+                  let balance = try erc20_balanceof.decodeReturnData(data)["0"] as? BigUInt else {
                 resultArray.append(0)
                 continue
             }