Fix a compiler complaint

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/render.c

@@ -1153,17 +1153,19 @@ bool init_render(session_t *ps) {
 
 	// Blur filter
 	if (ps->o.blur_background || ps->o.blur_background_frame) {
-		bool ret;
+		bool ret = false;
 		if (ps->o.backend == BKEND_GLX) {
 #ifdef CONFIG_OPENGL
 			ret = glx_init_blur(ps);
 #else
 			assert(false);
 #endif
-		} else
+		} else {
 			ret = xr_init_blur(ps);
-		if (!ret)
-			return false;
+		}
+		if (!ret) {
+			return ret;
+		}
 	}
 
 	ps->gaussian_map = gaussian_kernel(ps->o.shadow_radius);

src/utils.h

@@ -9,6 +9,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <unistd.h>
+#include <assert.h>
 
 #include "compiler.h"
 
@@ -29,6 +30,13 @@ safe_isnan(double a) {
 	return isnan(a);
 }
 
+/// Same as assert false, but make sure we abort _even in release builds_.
+/// Silence compiler warning caused by release builds making some code paths reachable.
+attr_noret static inline void BUG(void) {
+	assert(false);
+	abort();
+}
+
 /**
  * Normalize an int value to a specific range.
  *