Be resilient to when we get an exception while reading metadata.

src/Compilers/Core/Portable/MetadataReference/PortableExecutableReference.cs

@@ -162,6 +162,9 @@ internal Metadata GetMetadataNoCopy()
         /// Returns a copy of the <see cref="Metadata"/> object this <see cref="PortableExecutableReference"/>
         /// contains.  This copy does not need to be <see cref="IDisposable.Dispose"/>d.
         /// </summary>
+        /// <exception cref="BadImageFormatException">If the PE image format is invalid.</exception>
+        /// <exception cref="IOException">The metadata image content can't be read.</exception>
+        /// <exception cref="FileNotFoundException">The metadata image is stored in a file that can't be found.</exception>
         public Metadata GetMetadata()
         {
             return GetMetadataNoCopy().Copy();

src/Workspaces/Core/Portable/FindSymbols/SymbolTree/SymbolTreeInfo_Metadata.cs

 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Reflection;
 using System.Reflection.Metadata;
@@ -13,6 +14,18 @@ namespace Microsoft.CodeAnalysis.FindSymbols
 {
     internal partial class SymbolTreeInfo
     {
+        private static Metadata GetMetadataNoThrow(PortableExecutableReference reference)
+        {
+            try
+            {
+                return reference.GetMetadata();
+            }
+            catch (Exception e) when (e is BadImageFormatException || e is IOException)
+            {
+                return null;
+            }
+        }
+
         /// <summary>
         /// this gives you SymbolTreeInfo for a metadata
         /// </summary>
@@ -22,7 +35,7 @@ internal partial class SymbolTreeInfo
             bool loadOnly,
             CancellationToken cancellationToken)
         {
-            var metadata = reference.GetMetadata();
+            var metadata = GetMetadataNoThrow(reference);
             if (metadata == null)
             {
                 return null;
@@ -76,7 +89,7 @@ internal partial class SymbolTreeInfo
         {
             var unsortedNodes = new List<Node> { new Node("", Node.RootNodeParentIndex) };
 
-            foreach (var moduleMetadata in GetModuleMetadata(reference.GetMetadata()))
+            foreach (var moduleMetadata in GetModuleMetadata(GetMetadataNoThrow(reference)))
             {
                 MetadataReader reader;
                 try