Analysis should begin with function entry point

Author: mathcelo

slither/analyses/data_flow/engine/engine.py

@@ -33,7 +33,7 @@ def run_analysis(self):
         worklist: Deque[Node] = deque()
 
         if self.analysis.direction().IS_FORWARD:
-            worklist.extend(self.nodes)
+            worklist.extend(self.function.entry_point)
         else:
             raise NotImplementedError("Backward analysis is not implemented")