incorrect assignment of source file

[M-860307]

Describe the bug
In the t-SNE interface after loading two matrix.mtx data for scRNA analyses, the t-SNE interface could not colors the cells according to the source. When we colored the cells using the source choice, the t-SNE figure still exhibits one color, and the legend only shows one matrix.mtx data.

To Reproduce
As shown in the attached picture, we uploaded two matrix.mtx data and used the tSNE widget for visualization, but it could only visualize one matrix data.

Desktop (please complete the following information):

• OS: Windows 10
• Orange Version 3.22.0
• Add-on Version 3.5.0