Trap error from RPC callback rather than calling callback with its ow…

…n error (#9216)

* Trap error from RPC callback rather than calling callback with its own error

* add the actual error that occurred in the handler to the output

* use qx.core.Object's error() method instead of console's

* There was already a variable holding the context. Use it instead of a new one.

* for consistency, use qx.lang.Json instead of the natic JSON object, for now

framework/source/class/qx/io/remote/Rpc.js

@@ -568,7 +568,19 @@ qx.Class.define("qx.io.remote.Rpc",
             break;
 
           case 1: // async with handler function
-            handler(result, ex, id);
+            try
+            {
+              handler(result, ex, id);
+            }
+            catch(e)
+            {
+              eventTarget.error(
+                "rpc handler threw an error:" +
+                  " id=" + id +
+                  " result=" + qx.lang.Json.stringify(result) +
+                  " ex=" + qx.lang.Json.stringify(ex),
+                e);
+            }
             break;
 
           case 2: // async with event listeners