Auto merge of #18243 - DominoTree:18224, r=stshine

[18224] Check if line_count is zero to calculate space around line

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Check line_count before attempting to calculate space around line

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #18224 (github issue number if applicable).

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- [ ] There are tests for these changes OR
- [X] These changes do not require tests because changes are minimal and the error was triggered by a test

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components/layout/flex.rs

@@ -711,14 +711,18 @@ impl FlexFlow {
 
             line_interval = match line_align {
                 align_content::T::space_between => {
-                    if line_count == 1 {
+                    if line_count <= 1 {
                         Au(0)
                     } else {
                         free_space / (line_count - 1)
                     }
                 }
                 align_content::T::space_around => {
-                    free_space / line_count
+                    if line_count == 0 {
+                        Au(0)
+                    } else {
+                        free_space / line_count
+                    }
                 }
                 _ => Au(0),
             };