Add better error handling for failed loading of the LyShine shader (#6761)

Signed-off-by: abrmich <abrmich@amazon.com>

Gems/LyShine/Code/Source/UiRenderer.cpp

@@ -76,7 +76,7 @@ void UiRenderer::OnBootstrapSceneReady(AZ::RPI::Scene* bootstrapScene)
     // Create a dynamic draw context for UI Canvas drawing for the scene
     m_dynamicDraw = CreateDynamicDrawContext(uiShader);
 
-    if (m_dynamicDraw)
+    if (m_dynamicDraw && m_dynamicDraw->IsReady())
     {
         // Cache shader data such as input indices for later use
         CacheShaderData(m_dynamicDraw);
@@ -85,7 +85,7 @@ void UiRenderer::OnBootstrapSceneReady(AZ::RPI::Scene* bootstrapScene)
     }
     else
     {
-        AZ_Error(LogName, false, "Failed to create a dynamic draw context for LyShine. \
+        AZ_Error(LogName, false, "Failed to create or initialize a dynamic draw context for LyShine. \
             This can happen if the LyShine pass hasn't been added to the main render pipeline.");
     }
 }