Fix Grail Segfaulting on quit

[dkrautha]

I started walking through where things are dying when we try to quit, here's what I've found so far:

• [X] Failure 1 Cam is not initialized to a value in the constructor, so it points to a random place in memory unless the setLookAtProjection() function is called. This call doesn't appear to happen for things in 2D, so cam points to garbage. We try to delete a cam in the cleanup() function of Canvas, which gets called from the destructor of Canvas. If we try to delete garbage memory that isn't ours, we segfault.

Solution: Initialize cam to nullptr in the constructor of Canvas, and then check whether it is a nullptr before we try and delete it.

• [x] Failure 2 Dying withing the shader cleanup. The shader class has a static vector of all the shaders that have been created in the program, and a static cleanAll() function that iterates through and calls the cleanup() function on each. What the cleanup function does is call glDeleteProgram() with a parameter of the progID supplied by glCreateProgram when that is called. The call to glDeleteProgram() is what is segfaulting.

I'm not sure what to do to solve this, simply commenting out the glDeleteProgram() call does work, but it probably causes us to leak memory.

[dkrautha]

Solution for Failure 2: We were calling GLWin's cleanup() function twice, once at the end of the mainloop, and another in the destructor of GLWin. This led to calling glDeleteProgram() again on something a program that had already been deleted giving a segfault.

There are two options to fix this, either remove the mainloop call or the destructor call. The correct choice was to remove the destructor call as after calling cleanup in the mainloop, glfwTerminate is called which likely destroys the opengl context, and caused an immediate segfault in the destructor (you can't call an opengl function without an opengl context).