do not compile the first shader in the shader manager's constructor

This was crashing with the move of the V_Init2 call. Instead do it when we first render something so that we can open the window without immediately making the full backend operational.
This was only working on GLES because it performs lazy shader compilation.

src/common/rendering/gl/gl_shader.cpp

@@ -788,7 +788,6 @@ FShaderCollection::FShaderCollection(EPassType passType)
 	{
 		mEffectShaders[i] = NULL;
 	}
-	CompileNextShader();
 }
 
 //==========================================================================

src/common/rendering/vulkan/shaders/vk_shader.cpp

@@ -115,7 +115,7 @@ bool VkShaderManager::CompileNextShader()
 
 VkShaderManager::VkShaderManager(VulkanRenderDevice* fb) : fb(fb)
 {
-	CompileNextShader();
+	//CompileNextShader();
 }
 
 VkShaderManager::~VkShaderManager()

src/d_main.cpp

@@ -3262,6 +3262,7 @@ static int D_InitGame(const FIWADInfo* iwad_info, std::vector<std::string>& allw
 	if (!batchrun) Printf ("V_Init: allocate screen.\n");
 	if (!restart)
 	{
+		screen->CompileNextShader();
 		if (StartScreen != nullptr) StartScreen->Render();
 	}
 	else