Decouple the last part of step()

Windows/Debugger/CtrlDisAsmView.h

@@ -169,7 +169,7 @@ public:
 	void setCurAddress(u32 newAddress, bool extend = false)
 	{
 		newAddress = manager.getStartAddress(newAddress);
-		u32 after = manager.getNthNextAddress(newAddress,1);
+		const u32 after = manager.getNthNextAddress(newAddress,1);
 		curAddress = newAddress;
 		selectRangeStart = extend ? std::min(selectRangeStart, newAddress) : newAddress;
 		selectRangeEnd = extend ? std::max(selectRangeEnd, after) : after;

Windows/Debugger/Debugger_Disasm.cpp

@@ -208,14 +208,15 @@ void CDisasm::step(CPUStepType stepType)
 	ptr->setDontRedraw(true);
 	lastTicks_ = CoreTiming::GetTicks();
 
-	u32 oldAddress = cpu->GetPC();
-	u32 stepSize = ptr->getInstructionSizeAt(oldAddress);
+	u32 stepSize = ptr->getInstructionSizeAt(cpu->GetPC());
 	Core_PerformStep(cpu, stepType, stepSize);
 
 	Sleep(1);
+
 	// At this point, the step should be done, and the new address is just PC.
 	// Ideally, this part should be done as a reaction to an update message and not directly here.
 	// That way we could get rid of the sleep.
+	u32 oldAddress = ptr->getSelection();
 	u32 newAddress = cpu->GetPC();
 	if (newAddress > oldAddress && newAddress < oldAddress + 12) {
 		// Heuristic for when to scroll at the edge rather than jump the window.