add message to empty networks

[reimand0]

We should add a message to empty experimental networks where no interactions are present (PIK3CA). One reviewer pointed this out.

[krassowski]

Done. The message shows up for both:

• proteins where there are no interactions at all (example: PIK3CA) and,
• for such cases when we have some interactions but the active filters exclude all of them (e.g. methylation in BRCA1).

[krassowski]

This concern was earlier addressed in 70fd39e35a38ff6a0adffe4bda63a2cea9bcd665 too.

[krassowski]

I improved the message to address the empty predicted networks too: https://activedriverdb.org/network/predicted/NM_007294?filters=Mutation.mc3_cancer_code:in:GBM