#1339 fix another null case

Author: jantje

io.sloeber.core/src/io/sloeber/core/api/BoardDescription.java

@@ -626,6 +626,9 @@ public IPath getArduinoPlatformPath() {
             return null;
         }
         ArduinoPlatformVersion platformVersion = platform.getNewestInstalled();
+        if(platformVersion==null) {
+        	return null;
+        }
         return platformVersion.getInstallPath();
     }