fix crash with overlong textproperty above

fixes vim#12661

src/drawline.c

@@ -721,7 +721,7 @@ text_prop_position(
 
 	// add 1 for NUL, 2 for when '…' is used
 	if (n_attr != NULL)
-	    l = alloc(n_used + before + after + padding + 3);
+	    l = alloc(n_used + before + after + (padding > 0 ? padding : 0) + 3);
 	if (n_attr == NULL || l != NULL)
 	{
 	    int off = 0;
@@ -801,7 +801,7 @@ text_prop_position(
 
 		// n_attr_skip will not be decremented before draw_state is
 		// WL_LINE
-		*n_attr_skip = before + padding;
+		*n_attr_skip = before + (padding > 0 ? padding : 0);
 	    }
 	}
     }

src/testdir/dumps/Test_prop_long_above_1.dump

@@ -0,0 +1,8 @@
+|t+0#ffffff16#ff404010|h|e| |q|u|i|c|k| |b|r|o|w|n| |f|o|x| |j|u|m|p|s| |o|v|e|r| |t|h|e| |l|a|z|y| |d|o|g|.| |t|h|e| |q|u|i|c|k| |b|r|o|w|n
+>x+0#0000000#ffffff0@2| @56
+|y@2| @56
+|~+0#4040ff13&| @58
+|~| @58
+|~| @58
+|~| @58
+| +0#0000000&@41|1|,|1|-|6|1| @7|A|l@1| 

src/testdir/test_textprop.vim

@@ -3951,5 +3951,24 @@ func Test_error_after_using_negative_id()
   call StopVimInTerminal(buf)
 endfunc
 
+func Test_overlong_textprop_above_crash()
+  CheckRunVimInTerminal
+
+  let lines =<< trim END
+  vim9script
+  prop_type_add('PropType', {highlight: 'Error'})
+  setline(1, ['xxx ', 'yyy'])
+  prop_add(1, 0, {
+      type: 'PropType',
+      text: 'the quick brown fox jumps over the lazy dog. the quick brown fox jumps over the lazy dog. the quick brown fox jumps over the lazy dog.',
+      text_align: 'above',
+      text_wrap: 'wrap',
+  })
+  END
+  call writefile(lines, 'XtextPropLongAbove', 'D')
+  let buf = RunVimInTerminal('-S XtextPropLongAbove', #{rows: 8, cols: 60})
+  call VerifyScreenDump(buf, 'Test_prop_long_above_1', {})
 
+  call StopVimInTerminal(buf)
+endfunc
 " vim: shiftwidth=2 sts=2 expandtab