Crash when equipping wing cap on x64 branch (mesh.Begin called with 0 triangles)

[Supercoder219]

When Mario equips the wing cap on the x64 branch, the game throws repeated errors:

[G64] lua/entities/g64_mario.lua:499: called mesh.Begin with a bad primitive type (2) or count (0)

This happens immediately when the wing cap is equipped.

Cause:
GenerateMesh() can attempt to build the wings mesh with zero triangles when the wing vertex list is empty during the equip frame.

Fix:
Add guards to prevent mesh.Begin() being called with 0 triangles and reset wingsIndices every frame.

Patch included below.

local fLerpVector = LerpVector
function ENT:GenerateMesh()
	local interpolation = GetConVar("g64_interpolation"):GetBool()

	if self.MarioId == nil or self.MarioId < 0 then return end
	if vertexBuffers[self.MarioId] == nil then return end

	local vertex = vertexBuffers[self.MarioId][self.bufferIndex + 1]
	local lastVertex = vertexBuffers[self.MarioId][1 - self.bufferIndex + 1]

	if vertex == nil or lastVertex == nil then return end
	if vertex[1] == nil or lastVertex[1] == nil then return end
	if #vertex[1] <= 0 or #lastVertex[1] <= 0 then return end

	local posTab = vertex[1]
	local lastPosTab = lastVertex[1]
	local normTab = vertex[2]
	local lastNormTab = lastVertex[2]
	local uTab = vertex[3]
	local vTab = vertex[4]
	local colTab = vertex[5]

	if posTab == nil or lastPosTab == nil or normTab == nil or lastNormTab == nil or uTab == nil or vTab == nil or colTab == nil then
		return
	end

	local vertCount = #posTab
	if vertCount <= 0 then return end

	local hasWingCap = self.hasWingCap == true
	local mainVertCount = vertCount

	-- Reset wing index list every frame so stale data does not carry over
	self.wingsIndices = {}

	-- Only split off wing vertices if the model actually has them
	if hasWingCap and vertCount > 2256 then
		mainVertCount = vertCount - 24
	end

	-- Need at least one full triangle
	if mainVertCount < 3 then return end

	local triCount = math.floor(mainVertCount / 3)
	if triCount <= 0 then return end

	if self.Mesh and self.Mesh:IsValid() then
		self.Mesh:Destroy()
		self.Mesh = nil
	end
	self.Mesh = Mesh()

	if self.WingsMesh and self.WingsMesh:IsValid() then
		self.WingsMesh:Destroy()
		self.WingsMesh = nil
	end
	self.WingsMesh = nil

	local t = (SysTime() - fixedTime) / G64_TICKRATE
	local myColorTable = self.colorTable or g64types.DefaultMarioColors
	local col
	local uvOffset = 2 / 704
	local wingIndex = 1

	-- Main body mesh
	mesh.Begin(self.Mesh, MATERIAL_TRIANGLES, triCount)
	for i = 1, vertCount do
		if posTab[i] == nil or lastPosTab[i] == nil or normTab[i] == nil or lastNormTab[i] == nil or uTab[i] == nil or vTab[i] == nil or colTab[i] == nil then
			mesh.End()
			self.Mesh:Destroy()
			self.Mesh = nil
			return
		end

		if hasWingCap and vertCount > 2256 and i > vertCount - 24 then
			self.wingsIndices[wingIndex] = i
			wingIndex = wingIndex + 1
		else
			col = myColorTable[colTab[i]] or {255, 255, 255}

			if interpolation then
				mesh.Position(fLerpVector(t, posTab[i], lastPosTab[i]))
				mesh.Normal(fLerpVector(t, normTab[i], lastNormTab[i]))
			else
				mesh.Position(posTab[i])
				mesh.Normal(normTab[i])
			end

			mesh.TexCoord(0, (uTab[i] + 0.002) * 0.9968, vTab[i])
			mesh.Color(col[1], col[2], col[3], 255)
			mesh.AdvanceVertex()
		end
	end
	mesh.End()

	-- Wings mesh
	local wingsIndices = self.wingsIndices
	local wingsVertCount = #wingsIndices
	local wingsTriCount = math.floor(wingsVertCount / 3)

	if hasWingCap and wingsVertCount >= 3 and wingsTriCount > 0 then
		self.WingsMesh = Mesh()
		uvOffset = 0.5 / 704

		mesh.Begin(self.WingsMesh, MATERIAL_TRIANGLES, wingsTriCount)
		for i = 1, wingsVertCount do
			local j = wingsIndices[i]

			if j == nil or posTab[j] == nil or lastPosTab[j] == nil or normTab[j] == nil or uTab[j] == nil or vTab[j] == nil or colTab[j] == nil then
				mesh.End()
				if self.WingsMesh and self.WingsMesh:IsValid() then
					self.WingsMesh:Destroy()
					self.WingsMesh = nil
				end
				return
			end

			col = myColorTable[colTab[j]] or {255, 255, 255}

			if interpolation then
				mesh.Position(fLerpVector(t, posTab[j], lastPosTab[j]))
				mesh.Normal(fLerpVector(t, normTab[j], lastNormTab[j]))
			else
				mesh.Position(posTab[j])
				mesh.Normal(normTab[j])
			end

			mesh.TexCoord(0, uTab[j] + uvOffset, vTab[j] + uvOffset)
			mesh.Color(col[1], col[2], col[3], 255)
			mesh.AdvanceVertex()
		end
		mesh.End()
	end
end