Fixed #1003. Avoid crash when mask file is missing.

git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/trunk@14240 178a84e3-b1eb-0310-8ba1-8eac791a3b58

src/graphics/material.cpp

@@ -778,7 +778,6 @@ void Material::install(bool is_full_path, bool complain_if_not_found)
         {
             fprintf(stderr, "Applying mask failed for '%s'!\n",
                     m_texname.c_str());
-            return;
         }
     }
     m_texture->grab();