Backends: OpenGL3: Fixed zealous warning by initializing last_pixel_unpack_buffer. (#7614)

backends/imgui_impl_opengl3.cpp

diff --git a/backends/imgui_impl_opengl3.cpp b/backends/imgui_impl_opengl3.cpp
index 189371f..58603a0 100644
--- a/backends/imgui_impl_opengl3.cpp
+++ b/backends/imgui_impl_opengl3.cpp
@@ -750,7 +750,7 @@
     glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
     glGetIntegerv(GL_ARRAY_BUFFER_BINDING, &last_array_buffer);
 #ifdef IMGUI_IMPL_OPENGL_MAY_HAVE_BIND_BUFFER_PIXEL_UNPACK
-    GLint last_pixel_unpack_buffer;
+    GLint last_pixel_unpack_buffer = 0;
     if (bd->GlVersion >= 210) { glGetIntegerv(GL_PIXEL_UNPACK_BUFFER_BINDING, &last_pixel_unpack_buffer); glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0); }
 #endif
 #ifdef IMGUI_IMPL_OPENGL_USE_VERTEX_ARRAY