Pcbnew, export component placement: better string in menu (.gbr added).

Also fix 2 minor Coverity warnings.

eeschema/sch_view.cpp

@@ -163,7 +163,9 @@ void SCH_VIEW::DisplaySymbol( LIB_SYMBOL* aSymbol )
         if( std::shared_ptr< LIB_SYMBOL > parent = aSymbol->GetRootSymbol().lock() )
             drawnSymbol = parent.get();
         else
+        {
             wxCHECK( false, /* void */ );
+        }
     }
 
     for( LIB_ITEM& item : drawnSymbol->GetDrawItems() )

eeschema/symbol_editor/symbol_edit_frame.cpp

@@ -832,7 +832,9 @@ void SYMBOL_EDIT_FRAME::SetCurSymbol( LIB_SYMBOL* aSymbol, bool aUpdateZoom )
         if( std::shared_ptr<LIB_SYMBOL> rootSymbol = m_symbol->GetRootSymbol().lock() )
             rootSymbolName = rootSymbol->GetName();
         else
+        {
             wxCHECK( false, /* void */ );
+        }
 
         int      unit = GetUnit();
         int      convert = GetConvert();