Conditional breakpoint throws error when evaluating a complex expression. #316

Reproduce steps:

1. Add an expression such as message.toString() != null && message.toString() != null to a breakpoint.
2. When the code runs there, the evaluation will throw error "Breakpoint condition 'message.toString() != null && message.toString() != null' error: com.sun.jdi.InvalidStackFrameException occurred while retrieving value. ".

Actually evaluate the same expression at the standalone DEBUG CONSOLE view, it returns true. So the expression is acceptable. This looks like a bug of java debugger.