Backends: DX9: Fix potential resource leak (#4093)

backends/imgui_impl_dx9.cpp

@@ -157,16 +157,25 @@ void ImGui_ImplDX9_RenderDrawData(ImDrawData* draw_data)
     g_pd3dDevice->GetTransform(D3DTS_VIEW, &last_view);
     g_pd3dDevice->GetTransform(D3DTS_PROJECTION, &last_projection);
 
-    // Copy and convert all vertices into a single contiguous buffer, convert colors to DX9 default format.
-    // FIXME-OPT: This is a minor waste of resource, the ideal is to use imconfig.h and
-    //  1) to avoid repacking colors:   #define IMGUI_USE_BGRA_PACKED_COLOR
-    //  2) to avoid repacking vertices: #define IMGUI_OVERRIDE_DRAWVERT_STRUCT_LAYOUT struct ImDrawVert { ImVec2 pos; float z; ImU32 col; ImVec2 uv; }
+    // Allocate buffers
     CUSTOMVERTEX* vtx_dst;
     ImDrawIdx* idx_dst;
     if (g_pVB->Lock(0, (UINT)(draw_data->TotalVtxCount * sizeof(CUSTOMVERTEX)), (void**)&vtx_dst, D3DLOCK_DISCARD) < 0)
+    {
+        d3d9_state_block->Release();
         return;
+    }
     if (g_pIB->Lock(0, (UINT)(draw_data->TotalIdxCount * sizeof(ImDrawIdx)), (void**)&idx_dst, D3DLOCK_DISCARD) < 0)
+    {
+        g_pVB->Unlock();
+        d3d9_state_block->Release();
         return;
+    }
+
+    // Copy and convert all vertices into a single contiguous buffer, convert colors to DX9 default format.
+    // FIXME-OPT: This is a minor waste of resource, the ideal is to use imconfig.h and
+    //  1) to avoid repacking colors:   #define IMGUI_USE_BGRA_PACKED_COLOR
+    //  2) to avoid repacking vertices: #define IMGUI_OVERRIDE_DRAWVERT_STRUCT_LAYOUT struct ImDrawVert { ImVec2 pos; float z; ImU32 col; ImVec2 uv; }
     for (int n = 0; n < draw_data->CmdListsCount; n++)
     {
         const ImDrawList* cmd_list = draw_data->CmdLists[n];