Suggestions failed while spellcheck index build in progress when using AnalyzingInfixSuggester

All the search requests are failing during the window spellcheck index is built while using AnalyzingInfixSuggester

Observed in Solr 4.6.1

Reproducible steps:
1. Initialized spellcheck component with AnalyzingInfixLookupFactory
2. Consider the collection "test_suggest" (if not create one)
3. Lets have a dictionary file 'dictionary_a.txt' with size in MBs (~10MB). Each line contains a word (max 20char).
4. Now, do the following two things parallel,

• build the index : GET http://<solrhost>:<port>/solr/test_suggest/suggest_handler?spellcheck.build=true
• do the search : GET http://<solrhost>:<port>/solr/test_suggest/suggest_handler?q=dr
  Response : All the search requests are failing during the window spellcheck index is built.

Sample Configuration:
<searchComponent name="suggest" class="solr.SpellCheckComponent">
<lst name="spellchecker">
<str name="name">suggest_a</str>
<str name="lookupImpl">org.apache.solr.spelling.suggest.fst.AnalyzingInfixLookupFactory</str>
<str name="indexPath">./index/analyzingSuggesterIndex_a</str>
<str name="suggestAnalyzerFieldType">text_general</str>
<str name="sourceLocation">./dictionaries/dictionary_a.txt</str>
</lst>
</searchComponent>
<requestHandler name="/suggest_handler" class="org.apache.solr.handler.component.SearchHandler">
<lst name="defaults">
<str name="spellcheck">true</str>
<str name="spellcheck.dictionary">suggest</str>
<str name="spellcheck.count">30</str>
<str name="spellcheck.onlyMorePopular">true</str>
</lst>
<arr name="components">
<str>suggest</str>
</arr>
</requestHandler>