visualize is not woking on Mac App

Hi, I am trying latest commit of chisel in a Mac App, if I visualize a controller, it will fail with this error:
```
error: error: Execution was interrupted, reason: Attempted to dereference an invalid ObjC Object or send it an unrecognized selector.
The process has been returned to the state before expression evaluation.
Traceback (most recent call last):
File "/Users/taozhuang/Documents/chisel/fblldb.py", line 99, in runCommand
command.run(args, options)
File "/Users/taozhuang/Documents/chisel/commands/FBVisualizationCommands.py", line 247, in run
_visualize(arguments[0])
File "/Users/taozhuang/Documents/chisel/commands/FBVisualizationCommands.py", line 201, in _visualize
if objectHelpers.isKindOfClass(target, "UIImage"):
File "/Users/taozhuang/Documents/chisel/fbchisellldbobjecthelpers.py", line 13, in isKindOfClass
return fb.evaluateBooleanExpression(isKindOfClassStr.format(className))
File "/Users/taozhuang/Documents/chisel/fbchisellldbbase.py", line 145, in evaluateBooleanExpression
int(evaluateIntegerExpression("(BOOL)(" + expression + ")", printErrors)) != 0
File "/Users/taozhuang/Documents/chisel/fbchisellldbbase.py", line 133, in evaluateIntegerExpression
output = evaluateExpression("(int)(" + expression + ")", printErrors).replace(
AttributeError: 'NoneType' object has no attribute 'replace'
```

If I visualize [controller view], it will fail with this error:
```
error: error: :1:21: no known method '-view'; cast the message send to the method's return type
[responderChainItem view]
~~~~~~~~~~~~~~~~~~~~^~~~~
Traceback (most recent call last):
File "/Users/taozhuang/Documents/chisel/fblldb.py", line 99, in runCommand
command.run(args, options)
File "/Users/taozhuang/Documents/chisel/commands/FBVisualizationCommands.py", line 247, in run
_visualize(arguments[0])
File "/Users/taozhuang/Documents/chisel/commands/FBVisualizationCommands.py", line 189, in _visualize
"(unsigned long)CFGetTypeID((CFTypeRef)"
TypeError: can only concatenate str (not "NoneType") to str
```