workaround of an older nvidia bug added

src/ACGL/OpenGL/Objects/ShaderProgram.cc

@@ -118,6 +118,9 @@ SharedLocationMappings ShaderProgram::getAttributeLocations() const
     // reserve a string long enought for the longest name:
     GLint longestAttributeName;
     glGetProgramiv( mObjectName, GL_ACTIVE_ATTRIBUTE_MAX_LENGTH,  &longestAttributeName );
+
+    if (longestAttributeName == 0) return locationMap; // work around an old nvidia bug.
+
     char *name = new char[longestAttributeName+1];
 
     // get the name and location of each active attribute: