fix segfault when iks base requested on start is absent

+ if an iks base (e.g. given using -base and an invalid ip address) was absent on draw3 startup, and we chose not to try again connecting, draw3 would segfault on set-prober-address query
+ now we launch a draw3 instance with no data (and if the user clicks inside data widget, draw3 will fail on runtime assertion: "Cannot set invalid time!"), this behavior is consistent with the behavior when we open an absent base in a new tab

wx/draw3/database.cpp

@@ -95,6 +95,7 @@ void* QueryExecutor::Entry() {
 			q->prefix = last_prefix;
 		}
 		last_prefix = q->prefix;
+
 		Draw3Base::ptr base = nullptr;
 		try{
 			base = base_handler->GetBaseHandler(q->prefix);
@@ -104,8 +105,28 @@ void* QueryExecutor::Entry() {
 			delete q;
 			continue;
 		}
+
+		if (q->type == DatabaseQuery::ADD_PARAM) {
+			try{
+				base = base_handler->GetBaseHandler(q->defined_param.prefix);
+			}
+			catch(MissingBasePrefixException& e) {
+				sz_log(8, "base prefix missing %ls", q->defined_param.prefix );
+				delete q;
+				continue;
+			}
+			base->AddExtraParam(q);
+			continue;
+		}
+
+		// following query types require a valid base
+		if (base == nullptr) {
+			delete q;
+			continue;
+		}
 		switch (q->type) {
 			case DatabaseQuery::ADD_BASE_PREFIX:
+			case DatabaseQuery::ADD_PARAM:
 				// should not get here
 				break;
 
@@ -117,18 +138,6 @@ void* QueryExecutor::Entry() {
 				base->CompileLuaFormula(q);
 				break;
 
-			case DatabaseQuery::ADD_PARAM:
-				try{
-					base = base_handler->GetBaseHandler(q->defined_param.prefix);
-				}
-				catch(MissingBasePrefixException& e) {
-					sz_log(8, "base prefix missing %ls", q->defined_param.prefix );
-					delete q;
-					continue;
-				}
-				base->AddExtraParam(q);
-				break;
-
 			case DatabaseQuery::REMOVE_PARAM:
 				base->RemoveExtraParam(q);
 				delete q;