# HG changeset patch
# User Jonathan Kew <jkew@mozilla.com>
# Date 1432227274 -3600
#      Thu May 21 17:54:34 2015 +0100
# Node ID 383fdad2853cd3dfc7c17e8a86ff4c29dce128bf
# Parent  4858f16b05179f87f41cdbf5a8cc3b33b540513a
Bug 1167145 - Check result of PrevInFlow() before trying to call a method on it.

diff --git a/layout/generic/nsBlockFrame.cpp b/layout/generic/nsBlockFrame.cpp
--- a/layout/generic/nsBlockFrame.cpp
+++ b/layout/generic/nsBlockFrame.cpp
@@ -6142,18 +6142,20 @@ nsBlockFrame::ReflowPushedFloats(nsBlock
       next = f->GetNextSibling();
       prev = f;
     } // else: we did push |f| so |prev|'s new next-sibling is next.
     f = next;
   }
 
   // If there are continued floats, then we may need to continue BR clearance
   if (0 != aState.ClearFloats(0, NS_STYLE_CLEAR_BOTH)) {
-    aState.mFloatBreakType = static_cast<nsBlockFrame*>(GetPrevInFlow())
-                               ->FindTrailingClear();
+    nsBlockFrame* prevBlock = static_cast<nsBlockFrame*>(GetPrevInFlow());
+    if (prevBlock) {
+      aState.mFloatBreakType = prevBlock->FindTrailingClear();
+    }
   }
 }
 
 void
 nsBlockFrame::RecoverFloats(nsFloatManager& aFloatManager, WritingMode aWM,
                             nscoord aContainerWidth)
 {
   // Recover our own floats