Make monitormode detect_nan example not crash with random numbers

doc/tutorial/debug_faq.txt

@@ -343,9 +343,16 @@ can be achieved as follows:
 
     import theano
 
+    # This is the current suggested detect_nan implementation to
+    # show you how it work.  That way, you can modify it for your
+    # need.  If you want exactly this method, you can use
+    # ``theano.compile.monitormode.detect_nan`` that will always
+    # contain the current suggested version.
+
     def detect_nan(i, node, fn):
         for output in fn.outputs:
-            if numpy.isnan(output[0]).any():
+            if (not isinstance(numpy.random.RandomState, output[0]) and
+                numpy.isnan(output[0]).any()):
                 print '*** NaN detected ***'
                 theano.printing.debugprint(node)
                 print 'Inputs : %s' % [input[0] for input in fn.inputs]

theano/compile/monitormode.py

@@ -80,3 +80,14 @@ class MonitorMode(Mode):
         ret.pre_func = self.pre_func
         ret.post_func = self.post_func
         return ret
+
+
+def detect_nan(i, node, fn):
+    for output in fn.outputs:
+        if (not isinstance(numpy.random.RandomState, output[0]) and
+            numpy.isnan(output[0]).any()):
+            print '*** NaN detected ***'
+            theano.printing.debugprint(node)
+            print 'Inputs : %s' % [input[0] for input in fn.inputs]
+            print 'Outputs: %s' % [output[0] for output in fn.outputs]
+            break