Handling CFGs without load-param instructions in ControlFlowGraph::get_param_instructions()
Handling CFGs without load-param instructions in ControlFlowGraph::get_param_instructions()

Summary:
Currently an assert fires when calling `get_param_instructions()` on a cfg that has no load-param instructions (e.g., in a static method with no params), yet, there's no way to know before if a cfg has load-param instructions.
This diff returns an empty range in that case, instead of crashing

Reviewed By: justinjhendrick

Differential Revision: D19600740

fbshipit-source-id: b2d3632d9a5e37bd0784a5e3ed9cf058ae3254d5

facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex