Fix crash when pasting at buffer end

Fixes #4844

src/normal.cc

@@ -662,6 +662,8 @@ BufferCoord paste_pos(Buffer& buffer, BufferCoord min, BufferCoord max, PasteMod
     switch (mode)
     {
         case PasteMode::Append:
+            if (buffer.is_end(max))
+                return max;
             return linewise ? std::min(buffer.line_count(), max.line+1) : buffer.char_next(max);
         case PasteMode::Insert:
             return linewise ? min.line : min;

test/regression/4844-crash-on-empty-paste/cmd

@@ -0,0 +1 @@
+<a-o>Cpp

test/regression/4844-crash-on-empty-paste/out

@@ -0,0 +1,2 @@
+
+