Contact Test in "Node: Physics" test suite crashes after a few taps on the plus sign

[SvDyer]

Issues occurs in v3 branch (tried on Samsung Galaxy S III, SPH-L710, Android 4.3)

Steps:

1. Run CppTest > "Node: Physics" test suite > Contact Test
2. Tap on the '+' sign about 20 times (sometimes fewer taps would do it too if done fast)

Result: Test fails, CppTests app crashes

[minggo]

@Dhilan007
Could you please take a look.
Thanks.

[WenhaiLin]

Fixed at #8209