Clarified lazy initialization and added some thread sanity logic after discussion with @rgba16f

Gems/AtomLyIntegration/AtomFont/Code/Include/AtomLyIntegration/AtomFont/FFont.h

@@ -302,6 +302,7 @@ namespace AZ
 
         bool m_fontTexDirty = false;
         bool m_fontInitialized = false;
+        AZStd::atomic_bool m_fontInitializing = false;
 
         FontEffects m_effects;
 

Gems/AtomLyIntegration/AtomFont/Code/Source/FFont.cpp

@@ -106,6 +106,14 @@ bool AZ::FFont::InitFont()
         return true;
     }
 
+    // If we're being initialized in another thread, abort.
+    if (m_fontInitializing)
+    {
+        return false;
+    }
+
+    m_fontInitializing = true;
+
     // Create and initialize DynamicDrawContext for font draw
     AZ::RPI::Ptr<AZ::RPI::DynamicDrawContext> dynamicDraw = m_atomFont->GetOrCreateDynamicDrawForScene(GetDefaultViewportContext()->GetRenderScene().get());
 
@@ -129,6 +137,7 @@ bool AZ::FFont::InitFont()
     m_indexCount = 0;
 
     m_fontInitialized = true;
+    m_fontInitializing = false;
     return true;
 }
 
@@ -293,7 +302,11 @@ void AZ::FFont::DrawStringUInternal(
     const bool asciiMultiLine, 
     const TextDrawContext& ctx)
 {
-    InitFont();
+    // Lazily ensure we're initialized before attempting to render.
+    if (!InitFont())
+    {
+        return;
+    }
 
     if (!str
         || !m_vertexBuffer // vertex buffer isn't created until BootstrapScene is ready, Editor tries to render text before that.