Do not open a new tab for a dropped file, at least if it's the only one or first one of multiple files. Fixes issue #1764.

source/main.pas

@@ -4762,6 +4762,7 @@ begin
   // query-memo - load their contents into seperate tabs
   for i:=0 to AFiles.Count-1 do begin
     if fileExists(AFiles[i]) then begin
+      if i > 0 then
         actNewQueryTab.Execute;
       QueryLoad(AFiles[i], false);
     end;