[Client] Fix for truncation of strings with null in writeValue std::string overload

Author: boozer2

src/NimBLERemoteCharacteristic.cpp

@@ -712,7 +712,7 @@ std::string NimBLERemoteCharacteristic::toString() {
  * @return false if not connected or cant perform write for some reason.
  */
 bool NimBLERemoteCharacteristic::writeValue(const std::string &newValue, bool response) {
-    return writeValue((uint8_t*)newValue.c_str(), strlen(newValue.c_str()), response);
+    return writeValue((uint8_t*)newValue.c_str(), newValue.length(), response);
 } // writeValue