title: Check if uint8_t array is empty
body: <p>If I declare the following (which hold a HEX like {0x7E, 0x00, ...}):</p>
  
  <pre><code>uint8_t response[size];
  </code></pre>
  
  <p>And I print with:</p>
  
  <pre><code>void printHex(uint8_t* hex) {
  
    for(unsigned int i=0; i&lt;sizeof(hex)/sizeof(hex[0]); i++) {
      if(hex[i] &lt; 16) {
        Serial.print("0");
      }
      Serial.print(hex[i], HEX);
    }
  
  }
  </code></pre>
  
  <p>It prints this which I don't know from where it came:</p>
  
  <pre><code>0088FE3FF0FBFE3FA0382040A0ECFE3FAE10204001000000DCEBFE3FC033204018000000BC981800
  </code></pre>
  
  <p>Even though I've not initilized the variable with any value.
  The problem is that I cannot tell whether the variable has ben initilized with values or not. How to accomplish this? And why it prints the above without initilizing it?</p>