Fix GLES3 instanced rendering color and custom data defaults

(cherry picked from commit 6f88ed73be786e93e60a3c9dd4f9a4127badeba7)

drivers/gles3/rasterizer_canvas_gles3.cpp

@@ -1419,6 +1419,13 @@ void RasterizerCanvasGLES3::_render_batch(Light *p_lights, uint32_t p_index) {
 						glEnableVertexAttribArray(5);
 						glVertexAttribIPointer(5, 4, GL_UNSIGNED_INT, instance_stride * sizeof(float), CAST_INT_TO_UCHAR_PTR(instance_color_offset * sizeof(float)));
 						glVertexAttribDivisor(5, 1);
+					} else {
+						// Set all default instance color and custom data values to 1.0 or 0.0 using a compressed format.
+						uint16_t zero = Math::make_half_float(0.0f);
+						uint16_t one = Math::make_half_float(1.0f);
+						GLuint default_color = (uint32_t(one) << 16) | one;
+						GLuint default_custom = (uint32_t(zero) << 16) | zero;
+						glVertexAttribI4ui(5, default_color, default_color, default_custom, default_custom);
 					}
 				}
 

drivers/gles3/rasterizer_scene_gles3.cpp

@@ -2411,7 +2411,15 @@ void RasterizerSceneGLES3::_render_list_template(RenderListParameters *p_params,
 				glEnableVertexAttribArray(15);
 				glVertexAttribIPointer(15, 4, GL_UNSIGNED_INT, stride * sizeof(float), CAST_INT_TO_UCHAR_PTR(color_custom_offset * sizeof(float)));
 				glVertexAttribDivisor(15, 1);
+			} else {
+				// Set all default instance color and custom data values to 1.0 or 0.0 using a compressed format.
+				uint16_t zero = Math::make_half_float(0.0f);
+				uint16_t one = Math::make_half_float(1.0f);
+				GLuint default_color = (uint32_t(one) << 16) | one;
+				GLuint default_custom = (uint32_t(zero) << 16) | zero;
+				glVertexAttribI4ui(15, default_color, default_color, default_custom, default_custom);
 			}
+
 			if (use_index_buffer) {
 				glDrawElementsInstanced(primitive_gl, count, mesh_storage->mesh_surface_get_index_type(mesh_surface), 0, inst->instance_count);
 			} else {