[NFC] Fix uninitialized scalar field in constructor. (llvm#118324)

Non-static class field is not initialized in constructor.

Author: zahiraam

clang-tools-extra/clangd/index/MemIndex.h

@@ -97,7 +97,7 @@ class MemIndex : public SymbolIndex {
   // Set of files which were used during this index build.
   llvm::StringSet<> Files;
   // Contents of the index (symbols, references, etc.)
-  IndexContents IdxContents;
+  IndexContents IdxContents = IndexContents::None;
   std::shared_ptr<void> KeepAlive; // poor man's move-only std::any
   // Size of memory retained by KeepAlive.
   size_t BackingDataSize = 0;

clang-tools-extra/clangd/index/dex/Dex.h

@@ -146,7 +146,7 @@ class Dex : public SymbolIndex {
   // Set of files which were used during this index build.
   llvm::StringSet<> Files;
   // Contents of the index (symbols, references, etc.)
-  IndexContents IdxContents;
+  IndexContents IdxContents = IndexContents::None;
   // Size of memory retained by KeepAlive.
   size_t BackingDataSize = 0;
 };