ModuleAssistant: Fix warning, don't return bool as a pointer.

No functionality change intended.

llvm-svn: 192713
diff --git a/clang-tools-extra/modularize/ModuleAssistant.cpp b/clang-tools-extra/modularize/ModuleAssistant.cpp
index ba5d25f..45641cb 100644
--- a/clang-tools-extra/modularize/ModuleAssistant.cpp
+++ b/clang-tools-extra/modularize/ModuleAssistant.cpp
@@ -219,7 +219,7 @@
        I != E; ++I) {
     // Add as a module.
     if (!addModuleDescription(RootModule, *I, HeaderPrefix, Dependencies))
-      return false;
+      return NULL;
   }
 
   return RootModule;