When adding a new block group from the toolbox modal, only show blocks with no output connections.
When adding a new block group from the toolbox modal, only show blocks with no output connections.

rachel-fenichel/blockly,google/blockly,twodee/blockly,mark-friedman/blockly,joshlory/blockly,jstnhuang/blockly,google/blockly,rachel-fenichel/blockly,jano42/blockly,groklearning/blockly,LLK/scratch-blocks,google/blockly,nickmain/blockly,lzairdking/blockly,trodi/blockly,twodee/blockly,rachel-fenichel/blockly,jano42/blockly,rachel-fenichel/blockly,markocelan/blockly-minecraft,gengshenghong/scratch-blocks,groklearning/blockly,joshlory/blockly,hkoi/blockly,mark-friedman/blockly,markocelan/blockly-minecraft,carlosperate/blockly,jano42/blockly,hkoi/blockly,lzairdking/blockly,trinketapp/blockly,jstnhuang/blockly,nickmain/blockly,griffpatch/scratch-blocks,trinketapp/blockly,markocelan/blockly-minecraft,twodee/blockly,twodee/blockly,twodee/blockly,trodi/blockly,google/blockly-devtools,carlosperate/blockly,trinketapp/blockly,google/blockly-devtools,InspectorWidget/blockly,google/blockly,mark-friedman/blockly,rachel-fenichel/blockly,picklesrus/blockly,lzairdking/blockly,picklesrus/blockly,jano42/blockly,nickmain/blockly,LLK/scratch-blocks,gengshenghong/scratch-blocks,griffpatch/scratch-blocks,markocelan/blockly-minecraft,trodi/blockly,jstnhuang/blockly,twodee/blockly,LLK/scratch-blocks,LLK/scratch-blocks,mark-friedman/blockly,rachel-fenichel/blockly,trodi/blockly,trinketapp/blockly,mark-friedman/blockly,mark-friedman/blockly,carlosperate/blockly,InspectorWidget/blockly,rachel-fenichel/blockly,jstnhuang/blockly,joshlory/blockly,google/blockly,google/blockly,nickmain/blockly,lzairdking/blockly,gengshenghong/scratch-blocks,LLK/scratch-blocks,google/blockly,InspectorWidget/blockly,carlosperate/blockly,griffpatch/scratch-blocks,griffpatch/scratch-blocks,groklearning/blockly,gengshenghong/scratch-blocks,griffpatch/scratch-blocks,nickmain/blockly,nickmain/blockly,groklearning/blockly,picklesrus/blockly,gengshenghong/scratch-blocks,hkoi/blockly