Add sanity check for debug trace print statement (fix #1420)

ChangeLog

@@ -22,6 +22,7 @@
             Move default I2C bitrate to 100kbit/sec
             Linux: don't create a espruino.flash file if we're not writing to flash
             Add height check for Graphics.createArrayBuffer(...vertical_byte:true) (fix #1421)
+            Add sanity check for debug trace print statement (fix #1420)
 
      1v97 : nRF52: fix NRF.on('connect',...) issue
             STM32: Fix setDeviceClockCmd error for USB.setConsole()

src/jsvar.c

@@ -3314,7 +3314,7 @@ void _jsvTrace(JsVar *var, int indent, JsVar *baseVar, int level) {
   else if (jsvIsFloat(var)) jsiConsolePrintf("Double %f", jsvGetFloat(var));
   else if (jsvIsFunctionParameter(var)) jsiConsolePrintf("Param %q ", var);
   else if (jsvIsArrayBufferName(var)) jsiConsolePrintf("ArrayBufferName[%d] ", jsvGetInteger(var));
-  else if (jsvIsArrayBuffer(var)) jsiConsolePrintf("%s ", jswGetBasicObjectName(var)); // way to get nice name
+  else if (jsvIsArrayBuffer(var)) jsiConsolePrintf("%s ", jswGetBasicObjectName(var)?jswGetBasicObjectName(var):"unknown ArrayBuffer"); // way to get nice name
   else if (jsvIsString(var)) {
     size_t blocks = 1;
     if (jsvGetLastChild(var)) {