fix: avoid shader crash on null vector and negative x vector

scene/3d/cpu_particles_3d.cpp

@@ -881,9 +881,9 @@ void CPUParticles3D::_particles_process(double p_delta) {
 				case EMISSION_SHAPE_RING: {
 					real_t ring_random_angle = Math::randf() * Math_TAU;
 					real_t ring_random_radius = Math::randf() * (emission_ring_radius - emission_ring_inner_radius) + emission_ring_inner_radius;
-					Vector3 axis = emission_ring_axis.normalized();
+					Vector3 axis = emission_ring_axis == Vector3(0.0, 0.0, 0.0) ? Vector3(0.0, 0.0, 1.0) : emission_ring_axis.normalized();
 					Vector3 ortho_axis;
-					if (axis == Vector3(1.0, 0.0, 0.0)) {
+					if (axis.abs() == Vector3(1.0, 0.0, 0.0)) {
 						ortho_axis = Vector3(0.0, 1.0, 0.0).cross(axis);
 					} else {
 						ortho_axis = Vector3(1.0, 0.0, 0.0).cross(axis);

scene/resources/particle_process_material.cpp

@@ -635,9 +635,9 @@ void ParticleProcessMaterial::_update_shader() {
 		code += "		\n";
 		code += "		float ring_spawn_angle = rand_from_seed(alt_seed) * 2.0 * pi;\n";
 		code += "		float ring_random_radius = rand_from_seed(alt_seed) * (emission_ring_radius - emission_ring_inner_radius) + emission_ring_inner_radius;\n";
-		code += "		vec3 axis = normalize(emission_ring_axis);\n";
+		code += "		vec3 axis = emission_ring_axis == vec3(0.0) ? vec3(0.0, 0.0, 1.0) : normalize(emission_ring_axis);\n";
 		code += "		vec3 ortho_axis = vec3(0.0);\n";
-		code += "		if (axis == vec3(1.0, 0.0, 0.0)) {\n";
+		code += "		if (abs(axis) == vec3(1.0, 0.0, 0.0)) {\n";
 		code += "			ortho_axis = cross(axis, vec3(0.0, 1.0, 0.0));\n";
 		code += "		} else {\n";
 		code += " 			ortho_axis = cross(axis, vec3(1.0, 0.0, 0.0));\n";