Check for blank key coming from client

src/meshUtils.cpp

@@ -64,4 +64,13 @@ void printBytes(const char *label, const uint8_t *p, size_t numbytes)
     for (size_t i = 0; i < numbytes; i++)
         LOG_DEBUG("%02x ", p[i]);
     LOG_DEBUG("\n");
+}
+
+bool memfll(const uint8_t *mem, uint8_t find, size_t numbytes)
+{
+    for (int i = 0; i < numbytes; i++) {
+        if (mem[i] != find)
+            return false;
+    }
+    return true;
 }