Fix asserts with side-effects (per Keegan McAllister)

src/statesync/user.cc

@@ -20,6 +20,7 @@
 #include <typeinfo>
 
 #include "user.h"
+#include "fatal_assert.h"
 #include "userinput.pb.h"
 
 using namespace Parser;
@@ -75,6 +76,7 @@ string UserStream::diff_from( const UserStream &existing ) const
       break;
     default:
       assert( false );
+      break;
     }
 
     my_it++;
@@ -86,7 +88,7 @@ string UserStream::diff_from( const UserStream &existing ) const
 void UserStream::apply_string( string diff )
 {
   ClientBuffers::UserMessage input;
-  assert( input.ParseFromString( diff ) );
+  fatal_assert( input.ParseFromString( diff ) );
 
   for ( int i = 0; i < input.instruction_size(); i++ ) {
     if ( input.instruction( i ).HasExtension( keystroke ) ) {