message: Handle source variables that map to non-existant debug variables
diff: @@ -2857,6 +2857,8 @@ QString ShaderViewer::getRegNames(const RDTreeWidgetItem *item, uint32_t swizzle
  {
  const ShaderVariable *reg = GetDebugVariable(r);
  + if(reg)
  + {
  if(!reg->members.empty())
  return QString();
  @@ -2880,6 +2882,11 @@ QString ShaderViewer::getRegNames(const RDTreeWidgetItem *item, uint32_t swizzle
  ret += QFormatStr("%1.%2").arg(r.name).arg(xyzw[r.component % 4]);
  }
  }
  + else
  + {
  + ret += lit("-");
  + }
  + }
  prevRef = r;
  }
  