Fix crash caused by recently added assert about if string was set properly.

Memory Estimate is actually 31 characters length, str[31] is a null-terminator.

Return length of 31 for memory estimate property. Returning proper length
would lead to slowdown because of 2x iteration through vertices.

source/blender/makesrna/intern/rna_fluidsim.c

@@ -184,7 +184,11 @@ static void rna_DomainFluidSettings_memory_estimate_get(PointerRNA *ptr, char *v
 
 static int rna_DomainFluidSettings_memory_estimate_length(PointerRNA *ptr)
 {
-	return 32;
+#ifdef DISABLE_ELBEEM
+	return 0;
+#else
+	return 31;
+#endif
 }
 
 static char *rna_FluidSettings_path(PointerRNA *ptr)