Merge pull request esp8266#1948 from riyono/fix-bug-1940

added .c_str() to currentVersion

Author: igrr

libraries/ESP8266httpUpdate/src/ESP8266httpUpdate.cpp

@@ -220,7 +220,7 @@ HTTPUpdateResult ESP8266HTTPUpdate::handleUpdate(HTTPClient& http, const String&
     DEBUG_HTTP_UPDATE("[httpUpdate]  - current Sketch Size: %d\n", ESP.getSketchSize());
 
     if(currentVersion && currentVersion[0] != 0x00) {
-        DEBUG_HTTP_UPDATE("[httpUpdate]  - current version: %s\n", currentVersion);
+        DEBUG_HTTP_UPDATE("[httpUpdate]  - current version: %s\n", currentVersion.c_str() );
     }
 
     switch(code) {