Catch exception caused by invalid signature

mythril/analysis/report.py

@@ -165,12 +165,16 @@ class Issue:
 
         for step in self.transaction_sequence["steps"]:
             _hash = step["input"][:10]
+
+            try:
                 sig = signatures.get(_hash)
 
                 if len(sig) > 0:
                     step["name"] = sig[0]
                 else:
                     step["name"] = "unknown"
+            except ValueError:
+                step["name"] = "unknown"
 
 
 class Report: