Backends: WebGPU: protect better against zero tex id.

backends/imgui_impl_wgpu.cpp

diff --git a/backends/imgui_impl_wgpu.cpp b/backends/imgui_impl_wgpu.cpp
index 9a2aebb..1dc9309 100644
--- a/backends/imgui_impl_wgpu.cpp
+++ b/backends/imgui_impl_wgpu.cpp
@@ -551,12 +551,11 @@
                 ImTextureID tex_id = pcmd->GetTexID();
                 ImGuiID tex_id_hash = ImHashData(&tex_id, sizeof(tex_id), 0);
                 WGPUBindGroup bind_group = (WGPUBindGroup)bd->renderResources.ImageBindGroups.GetVoidPtr(tex_id_hash);
-                if (!bind_group)
-                {
-                    bind_group = ImGui_ImplWGPU_CreateImageBindGroup(bd->renderResources.ImageBindGroupLayout, (WGPUTextureView)tex_id);
-                    bd->renderResources.ImageBindGroups.SetVoidPtr(tex_id_hash, bind_group);
-                }
-                wgpuRenderPassEncoderSetBindGroup(pass_encoder, 1, (WGPUBindGroup)bind_group, 0, nullptr);
+                if (!bind_group && tex_id != 0)
+                    if ((bind_group = ImGui_ImplWGPU_CreateImageBindGroup(bd->renderResources.ImageBindGroupLayout, (WGPUTextureView)tex_id)) != 0)
+                        bd->renderResources.ImageBindGroups.SetVoidPtr(tex_id_hash, bind_group);
+                if (bind_group)
+                    wgpuRenderPassEncoderSetBindGroup(pass_encoder, 1, (WGPUBindGroup)bind_group, 0, nullptr);
 
                 // Project scissor/clipping rectangles into framebuffer space
                 ImVec2 clip_min((pcmd->ClipRect.x - clip_off.x) * clip_scale.x, (pcmd->ClipRect.y - clip_off.y) * clip_scale.y);