Fix case where shader type from file is unknown

The variable was previously uninitialized, so the value may not have
necessarily been zero for the comparison that follows.

src/common/shaderloader.hpp

@@ -200,6 +200,9 @@ int loadShadersFromFile(const char* file_path, struct ShaderRegistry *registry)
       else if(strcmp("geometry", type) == 0) {
          shader_type = geometry;
       }
+      else {
+         shader_type = 0;
+      }
 
       if(shader_type == 0) {
          // Invalid line, unknown type.