Fix language server crash when processing predefind macros. (shader-slang#2302)

Co-authored-by: Yong He <yhe@nvidia.com>
Co-authored-by: jsmall-nvidia <jsmall@nvidia.com>

Author: csyonghe

source/slang/slang-workspace-version.cpp

@@ -75,11 +75,15 @@ bool Workspace::updatePredefinedMacros(List<String> macros)
     {
         auto index = macro.indexOf('=');
         OwnedPreprocessorMacroDefinition def;
-        def.name = macro.getUnownedSlice().head(index).trim();
         if (index != -1)
         {
+            def.name = macro.getUnownedSlice().head(index).trim();
             def.value = macro.getUnownedSlice().tail(index + 1).trim();
         }
+        else
+        {
+            def.name = macro.trim();
+        }
         newDefs.add(def);
     }