Fix VV editing numeric entries in lists

- Previously attempting to edit a list entry with a Number value would runtime.  Unless you were in a particular set of circumstances, which could lead to even weirder effects like unexpected associatead values being set.
- Also cleaned up the experience by removing options from popup prompts that would inevitably lead to runtime errors.

code/modules/admin/view_variables/modify_variables.dm

@@ -97,9 +97,10 @@ GLOBAL_PROTECT(VVpixelmovement)
 
 	L += var_value
 
-	switch(alert("Would you like to associate a value with the list entry?",,"Yes","No"))
-		if("Yes")
-			L[var_value] = mod_list_add_ass(O) //hehe
+	if(IS_VALID_ASSOC_KEY(var_value))
+		switch(alert("Would you like to associate a value with the list entry?",,"Yes","No"))
+			if("Yes")
+				L[var_value] = mod_list_add_ass(O) //hehe
 	if (O)
 		if (O.vv_edit_var(objectvar, L) == FALSE)
 			to_chat(src, "Your edit was rejected by the object.")
@@ -179,12 +180,13 @@ GLOBAL_PROTECT(VVpixelmovement)
 	if (index == null)
 		return
 	var/assoc = 0
-	var/prompt = alert(src, "Do you want to edit the key or its assigned value?", "Associated List", "Key", "Assigned Value", "Cancel")
-	if (prompt == "Cancel")
-		return
-	if (prompt == "Assigned Value")
-		assoc = 1
-		assoc_key = L[index]
+	if(IS_VALID_ASSOC_KEY(L[index]))
+		var/prompt = alert(src, "Do you want to edit the key or its assigned value?", "Associated List", "Key", "Assigned Value", "Cancel")
+		if (prompt == "Cancel")
+			return
+		if (prompt == "Assigned Value")
+			assoc = 1
+			assoc_key = L[index]
 	var/default
 	var/variable
 	var/old_assoc_value		//EXPERIMENTAL - Keep old associated value while modifying key, if any
@@ -193,9 +195,10 @@ GLOBAL_PROTECT(VVpixelmovement)
 	else
 		variable = L[index]
 		//EXPERIMENTAL - Keep old associated value while modifying key, if any
-		var/found = L[variable]
-		if(!isnull(found))
-			old_assoc_value = found
+		if(IS_VALID_ASSOC_KEY(variable))		
+			var/found = L[variable]
+			if(!isnull(found))
+				old_assoc_value = found
 		//
 
 	default = vv_get_class(objectvar, variable)

code/modules/admin/view_variables/view_variables.dm

@@ -88,7 +88,7 @@
 		for (var/i in 1 to L.len)
 			var/key = L[i]
 			var/value
-			if (IS_NORMAL_LIST(L) && !isnum(key))
+			if (IS_NORMAL_LIST(L) && IS_VALID_ASSOC_KEY(key))
 				value = L[key]
 			variable_html += debug_variable(i, value, 0, D)
 	else