fixed forward SSR

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Debug/DebugDisplay.cs

                     children =
                     {
                         new DebugUI.Value { displayName = string.Empty, getter = () => "Click in the scene view, or press 'End' key to select the pixel under the mouse in the scene view to debug." },
+                        new DebugUI.Value { displayName = string.Empty, getter = () => "Warning: In forward only mode, debugging information may not be representative of the rendered pixel." },
                         new DebugUI.Value { displayName = "SSRay Model", getter = () => screenSpaceTracingDebugData.tracingModel }
                     }
                 };

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Debug/DebugDisplay.hlsl

 CBUFFER_END
 
 TEXTURE2D(_DebugFont); // Debug font to write string in shader
-RWStructuredBuffer<ScreenSpaceTracingDebug> _DebugScreenSpaceTracingData;
+RWStructuredBuffer<ScreenSpaceTracingDebug> _DebugScreenSpaceTracingData : register(u7);
 
 void GetPropertiesDataDebug(uint paramId, inout float3 result, inout bool needLinearToSRGB)
 {

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Lighting/Reflection/ScreenSpaceTracing.hlsl

     hit.positionSS          = hitPositionSS;
     hit.linearDepth         = hitLinearDepth;
 
-    bool hitSuccessful      = true;
+    bool hitSuccessful      = hitLinearDepth > 0;       // Negative means that the hit is behind the camera
-    if (input.debug)
+    if (input.debug && _DebugScreenSpaceTracingData[0].tracingModel == -1)
     {
         ScreenSpaceTracingDebug debug;
         ZERO_INITIALIZE(ScreenSpaceTracingDebug, debug);
         hit
     );
 
-    if (input.debug)
+    if (input.debug && _DebugScreenSpaceTracingData[0].tracingModel == -1)
     {
         // Build debug structure
         ScreenSpaceTracingDebug debug;