skip tracking elements without trackable sources

closes #1186 (closed)

see #1193 (closed) #1194 (closed)

• benchmark

====show====
master_results time: 6.85
traveltissues_1186-3_results time: 6.9
which is a +0.73% difference
master_results memory: 172.0
traveltissues_1186-3_results memory: 172.0
which is a -0.0% difference
====build-4====
master_results time: 743.5
traveltissues_1186-3_results time: 711.01
which is a -4.37% difference
master_results memory: 199.0
traveltissues_1186-3_results memory: 199.0
which is a -0.0% difference
====show cached====
master_results time: 15.63
traveltissues_1186-3_results time: 15.39
which is a -1.54% difference
master_results memory: 201.0
traveltissues_1186-3_results memory: 201.0
which is a -0.0% difference